Pixels can be configured to limit charging to 80% these days.

I’ve started using it and the difference between using 80% and 100% on a daily basis is negligible, I rarely if ever let my device go below about 35% anyway. So this change is basically free battery life for the device

They are most likely running an A/B test on exactly those metrics.

We’ll know if it’s successful if they roll it out in the end.