Question about my bf who is a purple belt in Bjj?

So my bf is a purple belt in BJJ and trains a lot for the last 5-6 years. He doesn’t brag about it but has mentioned that if it came down to a brawl on the street, he doesn’t see how the other person would have a chance unless they were an NFL linebacker or something.

Basically I’ve always wondered if he’s just being cocky or is he legit?

For reference I’ve never trained Bjj or ever been interested in it with the exception of him showing me some armbars or stuff in the living room for fun