You need to see some Bill Wallace fights. Who by the way was undefeated.
I saw Wallace fight in the 70s in his prime.
Wallace was a high school wrestler and has trained in bjj over the years.
Great kickboxer but in his prime days against a top wrestler or bjj Guy and with his bum leg I don't he would stay up.
It's been shown many times that those untrained in ground fighting get killed in cage matches.