I'd wager that there's some small feature you don't know about which uses audio input and it's requesting permissions too early rather than it being something malicious.

I wouldn't grant it either way though.

I switched to Firefox on Android recently and found that a lot of web sites with a login form, for some reasons, prompts for microphone on Firefox. This applies for major banks web sites like Wells Fargo as well. I suspect there's a common JS library being used by many sites for login forms that ask for microphone access early.

I've heard they integrated voice messaging, so could be that, but I'd want to explain myself on a website before asking for mic access.