Everyone talked shit about Ian Garry, he was everyone's joke. If Garry was ranked higher, Colby would fight him. Colby wants a title shot, beating Ian Garry doesn't do that. He's damned if he does, damned if he doesn't. So that's why that won't happen.
Colby has more bargaining room/leverage than Ian Garry for sure. It's not a question of fight Garry or fuck off. Those are not his options.
It comes down to this. He needs to beat a higher ranked opponent, he knows he can't beat Usman, but thinks he has a chance against Belal. That's it. Beating someone below him like Garry does nothing. If he wins, he should have. If he loses, he's done. Which would you do?
It will be more interesting to see what the UFC chooses or forces.