I wouldn’t really consider wildcat or trick plays to be true QB reps, so in that regard, I don’t think he’s taken any. He’s taken the RB spot and run with it (pun intended). He doesn’t need true QB reps to run a trick play or wildcat. He has arm strength and athleticism. My guess is that he simply wasn’t a good decision maker at QB. On a trick play, you need to only make 1-2 reads, which is something he can probably do just fine. It’s 4-5 reads from the pocket that he probably just wasn’t good at.
But yes, I’m sure they have implemented a few more wildcat/trick plays with Jackson and Johnson.