Let me pause to point out a glaring assumption here: Gruber is conflating the private beliefs and understanding of Apple’s senior vice president for software with the public statements of Apple’s senior vice president for software, and further, with the empathetic imagination of Apple’s senior vice president for software.
It was an emphatic, condescending, and sneering argument:
The single biggest misconception about iOS is that it’s good digital hygiene to force quit apps that you aren’t using. The idea is that apps in the background are locking up unnecessary RAM and consuming unnecessary CPU cycles, thus hurting performance and wasting battery life.
That’s not how iOS works. The iOS system is designed so that none of the above justifications for force quitting are true. Apps in the background are effectively “frozen”, severely limiting what they can do in the background and freeing up the RAM they were using. iOS is really, really good at this. It is so good at this that unfreezing a frozen app takes up way less CPU (and energy) than relaunching an app that had been force quit. Not only does force quitting your apps not help, it actually hurts. Your battery life will be worse and it will take much longer to switch apps if you force quit apps in the background.
Here’s a short and sweet answer from Craig Federighi, in response to an email from a customer asking if he force quits apps and whether doing so preserves battery life: “No and no.”
Just in case you don’t believe Apple’s senior vice president for software...
That is, I fully believe Craig Federighi. And knowing the complexities of technology, I believe that when anyone is answering a question like this, there's a range of possible answers and details. Craig Federighi's job, when asked questions by a tech reporter--even one who thinks he's above being told half-truths by the company he makes his living being close to--is emphatically not to let the conversation go into those rabbit holes. Believing him does not tell me whether his answer is fundamentally true, only that it's plausibly true.
Back to Gruber, ready with the deep sneering:
Like with any voodoo, there are die-hard believers. I’m quite certain that I am going to receive email from people who will swear up-and-down that emptying this list of used applications every hour or so keeps their iPhone running better than it would otherwise. Nonsense.
An awful lot of very hard work went into making iOS work like this...
And don’t even get me started on people who completely power down their iPhones while putting them back into their pockets or purses.
Let's start by pointing out that it is unquestionably correct for many people to power down their iPhones while putting them back into their pockets or purses to save power. Gruber knows this. But he's right that many people who do this don't know what a decent--imperfect, but decent--job iOS does of using little power while powered on with the screen off.
The question is tone. I suspect he's way overstating all of his points this way. And he shows you this, with sneaky footnotes that he can point to if people believe him too much:
Sometimes apps do use a bunch of battery in the background, and you're better off quitting them…In his fine print he even tells you to go to battery settings to figure out which ones are the wasting your battery while running in the background.
Yes, Apple aggressively pushes most apps to obey its published API. But they also aggressively design efficient hardware to make CPU use less of a concern to app developers, and they promote large (and Apple-friendly) players who make clever, often undocumented use of battery-hogging features. Whether you are a brand they feel advances their business is their primary concern. The OS could be far more aggressive about not letting apps use up CPU/battery (and data) in the background.
And it's probably good that they're not more aggressive! They make an informed tradeoff. But when someone with an older phone and OS version comes into the genius bar and says their phone is too slow and uses battery too quickly, and the genius shows them how to force quit apps that run in the background, the genius is probably helping, not promoting a pernicious myth.
Which, again, Gruber knows. Apple's own writing about iOS settings happily points out that lots of apps can suck up battery all day long running in the background. iOS developers know all the crap some apps do in the background that you can't do if the app has been force quit. And yes, iOS users have learned they have to force quit Swarm or Twitter or Candy Crush or whatever to save battery.
I do think it's true that most people who habitually force quit apps regardless of having noticed anything about battery life, as though that's just part of universal smartphone hygiene, don't need to do so. (I offer that in the spirit of "genuine investigation".)
And of course, this week has brought more from the don't-believe-Apple-or-quasi-Apple-mouthpieces like-Gruber dept. It appears that Apple has been secretly forcing their devices' performance to degrade over time, and of course Gruber has a defense of the practice.
There is an explanation for this that it is at least plausible (downgrading CPU when voltage drops can keep the device from crashing unexpectedly), but I wonder what portion of the overall motivation is really explained by this. Note that it has been observed on multiple generations of iOS and plugged-in Mac devices, not just the buggy 6S running on battery.
But I'm not here to slay Gruber. My point is that we should look out for when a writer is in a mental place where he's trying to figure out what's true and describe it and make his best recommendation--let's call that "genuine investigation"--and when the motivation is something else.
And we should be open to knowledge coming in many forms--some from the top down, some from the ground up. As with medicine, folk technology knowledge has unearthed many truths that show, in retrospect, we were wise to ignore experts--particularly ones paid to obfuscate.