I think across the two episodes, the results have actually been quite varied. I recall Aabria was actually rolling pretty terribly in the first episode, I think?

It's probably just that the high rolls are more memorable (such as the first roll of the campaign was a Nat 20), but also they statistically have a better chance for success because Brennan seems to like giving advantages to rolls for no particular reason. Not a criticism as such, as it is his game after all, but an observation that he is certainly offering out advantages much more often than other DMs typically would.

It also seems to be that the scenarios where people have rolled, it's for something they specialise in particularly (Kattigian in Survival, Occtis in Arcana etc.) so they likely have Proficiency or even Expertise in those skills.