Even the post that you quote tells that he can play multiple games at the same time and you are just repeating what he said. And also do you already try to do that on Blackjack.fun or you just suggesting without any basis because the game showing an error if you are playing multiple games with both quick results or fast games. The server is unable to connect and showing blackscreen when you do that like the error he is describing.
I think it is clear that you would be able to play if you have different browsers. Also this "multiple tabs" thing could mean that you would need multiple accounts, no idea if it is allowed. In that case you could do chrome, opera, firefox and whatever and you get to play on three different accounts all on the same time.
However, I still suggest that we shouldn't do any of this, just have one account and gamble only once without any trouble at all. There isn't a question of what will happen, it s going to be fine. This means that we should be focusing a bit more towards doing the right thing, and not try to find a wrong way to do something else.