Your question was why GPS permission is needed, you should now know why.
I am using MS Authenticator and Aegis. Using MS authenticator only for work accounts that have been setup for number matching feature, it is pretty nice to simply enter 2 digits in app than entering 6 digits in client itself any time you need to approve MFA.
Everything else that supports standard TOTP whether work related or personal is on Aegis - it is a much better TOTP app.