I think google is banking on the fact that despite all this, people will stay with them and give a very slim discount. But only once they complained loud enough. The do trade-ins all the time.
The thing is, bi-yearly phone replacements are not needed for most people anymore. Recent mid range phones can last double that.
Performance is good enough with modern SOCs. And new sets don't have new essential features, so keeping them alive for cheap is a no brainer for most. Especially if support is promised.
They skirted around it on the official doc. They didn't explicitly say not all 6a devices are affected. They instead say if yours is affected, based on where you got it from and what are the laws in your area, you might be eligible for compensation or free repair.
It is entierly possible that hardware lottery is in play and some batts are feom a different supplyer. From what I gathered.