Apple, on the other hand, went out and said “if you don’t buy a new phone we’re going to make your old phone run slower”. I think the battery life was just an excuse - did Apple really think its customers would rather have a slower phone than a phone with shorter battery life? Sounds ridiculous.

This isn't how that happened at all and is an example of why this was such a bad marketing fail. Apple simply reduced the turbo just enough that the phone wouldn't hitch or power off when the battery degraded. It was such a slight change it was literally only noticable by a very small shift in benchmark scores before and after a battery swap. They literally did a good thing for device longevity and got raked over the coals for it