Competing at lower rank in IBJJF comps

Been training for a few years and have been thinking about entering into the local IBJJF open comp. However, I was taking a glance at some of the guys that are entering under our team but from a different gym location and was surprised to see a guy I know is a purple belt listed under the blue belt division. I know the IBJJF registration is a pain in the ass and your prof has to sign off on it so maybe he isn’t able to register as a purple belt in the system yet which would be understandable. I also am not sure when he was awarded his purple but I know he’s at least had it a few months since I met him. I was just curious if this is something that regularly occurs or if the guy is straight up sandbagging/lying? Also, if you sign up for a comp months in advance and then receive a promotion in between are you required to inform them and change divisions? Either way I’m not going to tell, that’s his business but it did make me wonder.