It has its own rules and scoring and that has an effect on how participants grapple. Strikes obviously change things, but the absence of other techniques (up kicks, knees to a down opponent) definitely reduce the incentive to be in certain positions. 5 minute rounds. Scoring. It all matters.
I really think the training and focus of wrestling is the key. Wrestlers are thrown to the wolves from day 1. There are no white belt divisions. In practice, guys don't take it easy on beginners, they just beat the shit out them. It is competition focused. The attrition rate is absurd, but the survivors usually make a pretty strong competition team. BJJ is more focused on inclusion and teaching, it is not solely focused on competition. And that is pretty much the entire difference IMO.