Apple is known to slow older devices intentionally. They have admitted it.

https://www.bbc.com/news/technology-67911517

That’s the literal truth, but the subtlety behind it was that CPU spikes combined with low voltage batteries were causing phones to shut off. Apple’s slowing down the phone down was nominally because customers prefer slightly slower phones to phones that shut off unexpectedly. Should they have announced this as a feature and had a toggle switch to allow users that preferred the option to disable it? Of course. But I don’t necessarily think they did the wrong thing.