its very easy, particularly if your not kicking people very often or at all, to get abstracted from the purpise of a kick into the form of the kick, with out necessarily considering it purpose as prime.
and 5hats the way this is going.
the purpose of a kick is first to make contact, if that dorsnt happen any thing else is irelivant , and then to hurt them or at least cause enough worry about hurt to distract them whilst you do something else
the problem with spin kicks in general and this one in particular, is the extra movement substanialy reduces the likelyhood of making contract whilst not giving much if any extra umph and extra umph is no use if you dont make contqct.
so the whole question of is this a good spin kick need to be considered against, why are you doing a spin kick at all
if as seems likely its because of deficiences in his side kick or is it a back kick ? then thats the anwer right there,
now my hip issues means there, are some kicks i cant do, either at all or at least with any thing like good form enough to hurt , so i dont, they are dangerous to me
and other kicks that i do that arnt at all in the karate manual, that i do, just and only because they fit the criteria above
this had lead to some intresting chats with my instructor and other senior students about if they are really poor form karate or not karate at all, i care little, do they hit and do they hurt, yes, they will do for me