Jill is ex-Delta Force at like 24 and Chris retired from the air force ar 26. Wesker wanted the best of the best to police the suburbs, and/or test bioweapons.
Looking at the feat in question, Jill shoves Nemesis while he's recovering from a haymaker. It doesn't really contradict any showings up until then; she's nimble enough to dodge and he couldn't leverage his strength advantage.
Nemesis's durability has nothing to do with his lack of fighting skill. He also obviously survived the fall despite his lack of situational awareness in this incident.
now looking back at him.........outside of his soak and his persistence, nemesis really wasn't that incredible from a rumbles perspective. in terms of strength, he's about as strong as a fit man his size would be, seeing as how he was easily able to lift brad up with one hand and use a rocket launch with one arm. he's pretty fast for a guy his size but not so much that he's a blue to anyone else. he's durable but he can be driven off/stunned/incapacitated, so his soak has a limit how much damage he can take.
also, the less said about remake nemesis, the better.
One episode had the hulk bending the barrel of a tank like he was in some Bugs Bunny cartoon or something. Then he was able to push it back while it was trying to run him over.
There's also the infamous time he picked up and threw a bear through the air. There's also a few instances of him just lightly jogging straight through brick walls, not punching through, just putting his hands over his face and going right through them.
If Jill can push Nemesis and bullets can piece his skin, I see no reason why Hulk just couldn't pit his fists straight though Nemesis.
Most versions of the Hulk would actually toss Nemesis(OG and Remake) into the upper atmosphere with little effort.
Ichigo: What even *are* you?!
Kenpachi: Some say my mother was a train. Some say that I'm a rejected Godzilla monster too strong for the series canon. But everyone says: I'M THE KEEEEENPACHIIIIII!!!!