Why doesn’t Skype want to acknowledge working in Firefox?

Skype has a web interface at web.skype.com that implements both voip and video calls, alongside chatting, and it all works well. Officially, it claims to work only in Google Chrome and Edge.

Tech-wise, it works in Firefox 100%, but only under the condition that you locally change your user agent to either Edge’s or Chrome’s. In Opera, on the other hand, Skype works out-of-the-box (user agent intact), regardless that Opera isn’t listed as a “supported browser”.

I realise Microsoft is porting Edge to a Chrome-base, and i realise they wish you would use their browser rather than anything else, thus the bias towards Edge and Chrome is understandable. But having no warning in Opera sounds like a beef with Mozilla. Because if they had written their condition as “if user agent isn’t Edge or Chrome, show warning”, then it would have shown in Opera as well.

So is there some “strategic” reason for this?