So it is true that the site is legitimate and now there is no doubt about the mirror site because there is already some evidence that can be confirmed from the livechat above and in the official Betpanda discord.
And after I myself managed to enter this main site, and asked directly on livechat that it was indeed their official site so this has become an accurate confirmation with no more doubts.
I was about to post this but you already have. I've been using the Betpandacasino.io mirror link without any issues, it's indeed their official site. One difference I noticed is that Betpanda.io appears restricted in Greece, while Betpandacasino.io doesn't. So I'm guessing that's the reason for the alternative mirror? It can easily be confirmed without asking them, by signing in your account, a phishing link would sign you in whatever credentials you'd use. Anyway, I believe that the administration should mention both mirror links to avoid future confusions.