I suspect he's truly undecided. I don't see him going high in the draft and that could make his decision easier. He's also probably seen his brother's struggle just to get on the court and if he is not a 1st round pick then there's no guarantee he makes a team. And with his need to develop a shot that could add to the struggles.
Personally, I think he should come back and develop himself more. If he develops a shot, become even more physical, and can gain confidence offensive confidence in college - his draft stock will rise.