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)