On your first part, maybe you're right.
On the second part, so many Pixel devices are available used. Including older pixels that still have some support left. A new $1500 flagship Motorola won't be and the ones that do become used soon after will still be close to that price. I'm just saying I've bought quite a few used Pixels for just a few hundred dollars and I don't see that being the case for flagship Motorolas. It's great to have device options but I don't think GOS being locked to only flagship Motorolas is a great alternative, especially once Google locks Pixels out from being flashed.
People who are security-minded for the most part just want a device to handle daily tasks, etc. Not all the bells whistles of an expensive high-end phone. If thats what people want in their phone, that's great, everyone has their need or desires for what they want in a phone but that being the only option will put GOS out of reach for many.