Fitbit users will be required to log in with their Google account from 2023, according to https://hackertimes.com/item?id=32963273

The same thing happened when Facebook acquired Oculus and consumer protection agencies as well as users everywhere started throwing a fit.

I think Facebook backed off pretty quickly?

I wouldn't say it was "pretty quick". It took them two years IIRC. They introduced it with the Quest 2 as a requirement and only lifted it earlier this year.