Most prospects in that situation opt to return to school -- a total of 130 players have withdrawn from the draft in the last two years. But 47 of those players have opted stayed in the draft despite no combine invitation. None of those 47 players were drafted.
I don't know where Bowman's head is or what the teams are telling him, but the odds are not in his favor. He is looking at being an undrafted free agent or maybe a second rounder. That is a tough road to make in as a NBA player. As unfair as the system might be, I think another year at BC is better than the G League or going to Europe.