For example watch this guy's (rosafield) P-2 nomo speedrun here, you can see that he just shotgun swaps even tho hes just flying, do speedrunners do this because they're just bored or do they do it for another reason
Shotgun swapping adds a very minimal amount of speed (1u/s) while mid air. I'm pretty sure it actually makes no difference at ub speeds but it can make a noticeable difference at anything under that (don't quote me on that though lmao I am not a tech expert)
If you have not seen ULTRAKILL is finally having a speedrunner competition for real money!!! It starts in about four hours from the time I am making this news post, in fact its probably already started when you are reading this so click the challenges widget on the right and read up on the rules and