You are talking about two different things. One is people leaving GBP to fight Manny with the OK given by GBP then coming back to GBP both of which are partners in GBP. The other is a fighter leaving to go to 50 and then trying to fight GBP fighters. Two way different scenarios.
That's because it made business sense to continue the relationship beyond the severance. Your contending that GB could possibly blackball Broner if he were to leave them, which is conceivable I suppose. What I'm simply saying is that they've demonstrated that they are capable to doing business with a fighter once they've departed from their company. Also, to those asking about a link to the JMM-Canelo story, the seen posted an article a few days ago in which JMM stated that he wasn't interested in fighting Canelo. There's also been talk on the net about GB offering JMM the opportunity. Sorry, no link.
Sure they did but look at the context. Mosley and Marquez are GBP partners and the only reason they left was for a fight with Manny.
JMM-Fedchenko was a Top Rank promoted fight. As will JMM's next fight even if it's not against Pac. And, TBH, if what you say is true and JMM still is a GB partner, I'd be somewhat shocked.
Broner hasn't even showed he can sell a PPV. I think Donaire is at the point where given the right fight he can sell a PPV. He's there. Canelo has been there for a while too. Ward isn't there yet but neither is Broner.