Bicycle kick and hover come to mind, stanky leg has been mentioned. Erron Black 21122 and Kung lao 112124 also apply. Don't forget there are multiple instant air specials that can nearly totally overshadow their ground specials.
Not to say that command grabs are the only arbitrarily verbose command.
Though for certain commands they are not
arbitrarily difficult, they're as difficult as they need to be, and that's whats important. 21122 for Erron Black is frustrating, but just based on the speed of the punches and NRS's "dial in" system, they're difficult because that's just how it has to be for the move to work.
Pretty sure bicycle kick is a good example of a move that has extra motions tacked on 'just cuz' though.
So the question is, do grabs
need to have that input to function as they should, or is it an extra button press 'just cuz'. I think in most cases it's the latter.
I think these are legitimate reasons for complex inputs:
1. You have limited controller space and inputs, so sometimes that extra motion is needed to differentiate.
2. Motions are often required so special inputs are affected properly by crossups.
3. Sometimes a move is meant to come out super fast when buffered, but to have some startup when not buffered (Shoryuken's in SFIV for example. 3 frame startup for excellent reversal, but it takes around 14+ frames to input the motion naked. Also, Gief's grab in SFIV)
4. The speed of the move and consequences of the way the controls just work naturally make it difficult, basically Erron's 21122
I don't think Jason's grab fits into any of those categories really. I don't think any command grabs in MKX do actually.