I honestly think they didn’t disclose it precisely because there was no malicious intent behind it. It was something they did to extend the useful life of the phone, and I don’t think it occurred to them that it would be seen negatively.
It also doesn’t make sense as a shady tactic to spur phone upgrades because you can always just get a battery replacement to restore the original performance. You don’t need a new phone, just a new battery.
I’ve worked at a few places with “unlimited PTO” and I totally agree.
It sounds great in practice: “as long as your work is getting done, take as much PTO as you want!” In reality, it never works out that way because there’s never a “good” time to take a vacation; if you don’t have vacation days that you have to use, you won’t use them.