You know for sure how the power-management code works in every Android device ever produced?
You're literally proving the point here. There's much, much more transparency on the Android side of things. Custom ROMs and the stock Google Android images have been combed over for almost the last decade by loads of different individuals and groups around the world. Now, we surely don't control the Samsung-esque bloatware that they slap on top of stock Android, but there's absolutely no way there's throttling code that lives in Android that we don't know about yet.
Anecdotal evidence of my own: I have a Nexus 5 that's nearly 5 years old now that my kids use daily. It's using a stock Lineage ROM. The battery certainly isn't the best anymore, but the phone doesn't feel different than the day I bought it, and it doesn't crash.