There's no way taking a 21 day turnaround is actually easier unless your completely undisciplined with your diet between fights and need that 2nd date to stay engaged mentally. Even in a fight where it looks like a fighter took zero damage, I guarantee you they still sustained damage in the fight. Perez actually out landed fig and hit him with a mean leg kick(Perez has brutal leg kicks).
There's no way Fig actually prepared properly for this fight, he had the same thought most people did. That he didn't really need to, that he would run through Moreno and studying tape and proper game-planning would take a backseat.
21 days is nothing, you honestly need to rest for atleast 7 and that's assuming everything went perfect, then you need to begin your meal plan for the next two weeks. Hard sparring is completely out of the question, and watching what footage you can for preparation will take up the rest of your time. I don't think Fig was at his best for this fight, I don't think any fighter in the modern era can be with just 3 weeks between fights.