And [according to that site], outside of the 5 teams that take a majority of their snaps under center, 9 other teams take at least 40% under center. So that's 14 teams that take at least 40% of their offensive snaps under center. Which is a pretty significant number. That's more than a few handoffs and pitches. Mind you some teams only really go exclusively shotgun on 3rd & longs, when they're down big, or in 2 minute drills at the end of halfs.
I don't think Jalen is completely incapable of running anything other than Lincoln's system but I'd be worried about him going to a team that's not going to completely build around what he's good at like Lamar. Sometimes these NFL coaches are stubborn and want to force players to play the way they want them to play, instead of play in a way that's the best for the player.
It also doesn't remove snaps under center that are clocking the ball, kneel downs and obvious running out the clock situations.
Here are the teams using under center the most. Last number in parentheses is percentage of total plays that are passing plays from under center. It doesn't give how many steps are in the drop though. (3-5-7)
Minnesota, 71% snaps under center and 35% are passing plays (24% total)
San Fran, 58% (32%) (18% total)
Rams, 54% (35%) (19% total)
Oakland, 52% (29%) (15% total)
Tennessee, 51% (30%) (15% total)
That's a decent chunk but most teams are between 10-12% of total plays are passing plays under center. He would need to tighten that up for sure but he's shown he can adapt to any offense he's had.
I completely agree with your second point though. Coaches/GMs with an agenda are dangerous. I'm hoping he ends up in Pittsburgh though. Big Ben should be done in a year or two.