I think these things are not casual. That is, they occur with the same frequency that you can get a special legendary in a free box (for ex). But they are programmed into system, it’s luck and it can touch anyone.
I think that’s the case, because, in the previous version, there was even an achievement that said something like “win a battle for 1 point”.
It’s luck, but it’s not casual. I think that in the 2 years I have played, maybe it happened to me 2 or 3 times, if I remember.