I think that a shooter fits any system. I will say that Underwood has mentioned many times that he values versatility and prefers big guards, neither of which are JCL.
Yea, when Underwood got here I heard some say how much it would benefit JCL. But Underwood's offense is predicated on freeing up space and getting to the basket, which is the weakest part of JCL's offensive game. Sure, open shots will be created in Underwood's offense, and an overall boost in off. efficiency is good for everyone on the team (rising tide lifts all boats), but I don't think JCL stood to gain disproportionately.
My assumption is that JCL had a tight bond with Groce, and between his exit and the influx of guards coming in, he decided he was best served going elsewhere. That's certainly his prerogative as an amateur athlete.
Here's hoping we don't block the kid from going to DePaul or ND or wherever else he wants to play. Regardless of the reason, it just comes off as spiteful. Google "Cam Johnson" for proof.