By itself, this throttling is a good thing and keeps phones usable for longer, because a phone that is slow is better than a phone that randomly reboots.
The problematic part was that they a) didn't disclose it, and b) did this for phones within the warranty period, so instead of the phone visibly crashing and you returning the obviously broken phone, it just lost performance which you might not have noticed in time to get a free replacement.
> XDA user XCnathan32, along with assistance from two other users, created the fix and put it up for anyone to give it a whirl. Without getting too technical, the fix shuts down all four of the Nexus 6P octa-core Snapdragon 810 processor’s performance cores that seemingly prevent the phone from properly booting
https://www.androidauthority.com/nexus-6p-bootloop-fix-78930...
People definitely complained about the random reboots, especially on the Nexus 6P, since that phone wouldn't boot again until after it was connected a charger plugged into a power outlet.
Heaven forbid you had a medical emergency away from a power outlet with a phone that unreliable.
Google just refused to do anything about it.
It soft bricked itself until you were able to plug it back into a power outlet.
Until then it was useless.