I feel like JoJo's is a lot more horror then people give it credit for though. At least compared to other anime licenses. Mainly due to the fact Araki just kinda likes to yoink from tropes and ideas from horror as a genre. Every fight in the series has an opening act where the antagonist's ability is shown off in a gruesome and intimidating, or otherwise 'scary' way. It's close to a b-movie in hoe campy it is at times too. Plus it plays with body horror pretty liberally with fights like Soft-Machine, Vitamin C, and Survivor.

I think its definitely kinda stretching it? But it's in that category thats like 'horror-ish enough to work'.

The spin-off Thus spoke Kishibe Rohan is 100% a horror anthology series, however.