The Google Play Integrity API was added as an authentication method for the MLPA backend. I surfaced these APIs to the team to see if we can use it [Android Attestation API] as an alternative method to the play integrity APIs.
3 months ago - 2016895 - Use Android Hardware Attestation instead of Google Play Integrity API
The intention is to block fraud against Mozilla’s services. We do not want our costly server infrastructure that powers Firefox to be misused by bots. Therefore, we require a Mozilla Account. If you do not use a Mozilla account, we fall back to signals from the Operating System (in this case: Android). That is all. The signal is not required, because we will always trust a Mozilla Account.
6 days ago (not from Firefox Android team) 2046154 - Feature Request: Google Play Integrity seems anti-ownership, anti-user, and proprietary anti-competitive and I suggest you consider a removal
This has some more discussion on the topic