I am curious what is the basis for this

No need to yell. Some basic etiquette does apply to the forums posting.
Now, if you haven't noticed over the years, the game will always be biased towards people who pay to win because, in most cases, they get better cards than the majority of the player base, and it has been like that since day one.

Anyway, the VSA basics are as follows: You get 90 seconds to score goals, play locally against an exact copy of your opponent's squad, and vice versa. Once both players 90 seconds are up, it compares the scores you both got, and then it shows you both what you ended up getting. Some in-game visual updates seem to be in real time, where you see opponents' goals, but it's an asynchronous update, which means it's not real-time and you don't really get to see the actual score until it's posted after the game. Your chances are also generated in groups of 10, so you pretty much always have some leftover chances from the previous game, but it overall balances out in the end.

Lastly, there are known issues with the chances distribution where many of the basic chances are actually good chances and EA devs know about it. It's being investigated, but there is no ETA on resolution at this point in time.