I agree with this assessment. Any 2 supernatural beings against each other is essentially man vs man. Them fighting involves agency, otherwise it’d be too boring to make a story about.

If we had 2 reanimated skeltons swordfighting, it would be cool for a couple minutes, but they can’t talk, they can’t plot and scheme, and they’d just keep on fighting with no purpose or end. Not a great story.

I don’t know the origins of the Castlevania vampires, a quick look shows many origins, but the Vampire Chronicles vampires still seem very much man vs man. IIRC, they basically are just regular people essentially possessed by part of an original Egyptian demon. When the demon part of them is killed, that’s why they just die. So for plot purposes, they’re just guys with a chronic illness. They still retain all the characteristics and associated drama of the people they were when they were alive.