Doesn't it have something to do with the bad experience he had with former Quartier Latin-members (CNN & Champion) ?

never, he rejected equaliseur,kanza despite being seguin's brother,rejected eric ibrahimovic even kabuya when he was never in europe tours and approached bcbg to join since pajo and  benladen were never taken to tours ei
ther so he tough he had a chance with kokoso animation which made him famous
for whatever reason he likes to stick to that system strongly, even tolbert solo had it hard to join until he convinced jb that he was not really a kabose group member but rather a session artist who was helping him out and playing in albums of almost everybody in studio in the same time

One of the problem of JB is this stupid rethoric that he does. I meam he was rejecting Tolbert lol. If he had rejected him ee would never have Tetuka, Correction, Nguzama and so on. So imagine if he took Kabuya. BCBG would have been a powerhouse and could seriously be a threat to Fally's power with Fusee, Kabuya, Tolbert but JB seems like he doesn't care about being competitive anymore

It is very tough to the join BCBG from another big band period.

Some guys leave bands stay under the radar for years then try to convince that they are joining from the cold not other bands. "Poaching is a no no "