I get his reluctance but it might prove to be a stupid move.
UFC does not want to give him a titleshot after pulling out. Khabib, Tony, Charles, etc. they all had to re-earn that titleshot.
Beating Gamrot not only gets him right where he needs to be, he also avenges that one loss on his record.
His titleshot has been delayed as it is, pissing off the UFC by pulling out last minute plus now refusing to re-earn the titleshot won't help him at all.
On the flipside he might want to angle for a bigger fight, since beating Gamrot might not move him forward much. This is why I 100% believe he should rematch Charles if they do indeed make Islam vs Ilia.
Otherwise figure it out between Islam, Ilia, Charles and Arman. Those four have to be matched up against eachother some way.