This is a poor comparison. The decision with Monahan was whether or not he would develop more in the NHL or CHL, he was clearly not going to develop much in the CHL being so far ahead of the other players in that league. The AHL was not an option. I would argue that if it was, we would have seen Monahan in the AHL for at least part of this season.
With Johnny G, the decision has to be whether or not he will develop more in the NHL or AHL, both pro leagues, both above what he is playing at currently in the NCAA. Unless he decides to finish his last year at college, of course.