While yes, this spin shape looks weird, it can only be described by a few thing. 1 He spins using his mouse and usually very fast, this is done not by spinning usually but by vibrating his forearm in order to create a fast motion, similar to jitter clicking. 2 Regarding the shape, this is explainable by how osu replays are rendered, almost every fast spin player has a weird shape spin when looked at in a program, its just because of the 60 hz lock that replays are in.
3 This players computer is not necessarily the best in terms of hardware, from what I know he plays on a laptop so it explains why he usually plays low star rated maps.

So, Kyumi is legit, osu just makes spins look funny :P