Nothing wrong with it at all ... NJCAA doesn't participate in the NLI process. There is nothing wrong with a players agreeing to play at a JUCO and a 4-year institution and then making up his mind at the last minute (legally, nothing wrong, ethically, it's a bit questionable).
Now, if you have two 4-year colleges, both which participate in the NLI program, College A has made an offer and the player has given his verbal commitment too ... yet College B, knowing the player has already given his verbal commitment, still goes ahead and makes him an offer .... now I've got a problem with the coaching staff at College B in that situation.
4-Year versus Juco is comparing apples to oranges. No problem there. Grades might force a player's hand or getting drafted and offered a DFE might force a players hand.