I think that in practice, that applies to only the privacy sensitive features. Would you be upset if suddenly they rolled out a feature that reduced battery consumption by 10%?
This particular case was obviously a bug, but I suppose every software manufacturer is continuously doing A/B testing, and 99% of time the user would not even notice. I would be surprised if Google was not doing A/B testing, and did not have the whole framework for doing it.
If you're talking about battery saving mode, I would be upset if they activated the feature (turning it on) without my consent, yes. I don't have issues with Google pushing improvement to their code via OS updates.
If they secretly installed it, of course I would be. It's not like this is the only way to deliver features...
On live (not beta), unsuspecting users, without their consent?
From my perspective there shouldn't be a problem for Apple to have the regular updates work as you describe. And also for them to have an alternative method they can use without any user intervention at all. (Which probably very seldom is used.)
anecdotal story with absolutely zero proof
If you lack real control over your device, "absolutely zero proof" is the new normal, and everything that gets zeroed out of RAM is rendered anecdotal thusly.