I agree with pretty much every thing you've said, but with one caveat. I've watched a bit of his high school tape and all of his snaps at Texas. I think he is actually a sophisticated pass rusher, but is still working out what he can and can't do as a college freshmen. He used the basic rip move pretty well in high school and was happy to bull rush, but has avoided those at Texas, which is probably smart. He's not strong enough (yet) to bull rush most OTs he'll face and the rip move is really more useful after you've gotten tangled up with the tackle - something he's avoided as much as possible. I've haven't really seen him use the swim move in college or high school, but maybe that's because he doesn't like giving the tackle a chance to get under his pads. I think he's been relying primarily on speed rushing because that's the advantage he has at this point in his game and at this level.
But I recommend watching his feet. He very good at playing the "game within the game" against the OT across from him. He'll use a stutter step inside in a series after the OT scene a stunt or two, making the OT pause and lean inside just enough to give Simmons an easy path around. He'll also change his pace up from down to down, making it harder for the OT to get into the same rhythm.
To be clear, he's still playing like a freshman. But his pass rush is probably a little more developed/sophisticated than it seems so far this season.