The concern is that they "aren't authorized apps". As I've read it, this is a proxy for "we aren't certain these apps can be trusted, but nobody ever got fired for pointing the finger at Mozilla or Google when something goes wrong, but would be fired if they pointed it at this one random guy in the Netherlands".
I could not get audio on Firefox
It was the only site I ever found where I could not get audio and I suspect some Google malfeasance
When I initiated a meeting I used Jitsi, no such troubles