I'm not sure why you think he's more likely to pick up "bad habits" if he stays in France. That seems a little unfounded.
The Celtics have scouts and staff who would be tracking his development pretty closely there.
most of that post was asking questions,i watched the red claws with dwight powell and when rj was up there-
my sons premier league team supplied some practice and end of bench guys for a pro team here in england-
i have no way of comparing d league to france or france to spain or at what level that yabusele played or the coaching and facilities-
this post was written to hopefully get answers
it would be easy to pick up bad habits,all you hear is how fast summer league is to college
an example might be slow release or low release that might not work against NBA length
as to coaching my sons coach also had coached one of the pro teams in england witha bunch of american players
my sons team produced an all england guard and another that went to play for real madrid-at 16 and under his squad lost in finals of final four in last two minutes-i attended every practice game and tournament-canary islands,mainland spain his team beat the italians and lost to barcelona and did well against real madrid---i thought the red claws were a model with good coaching and fast commute to waltham or home games-