They SHOULD have called it Prom Night 5!
It's not a remake, and it feels more like one of the sequels, where the only thing that connects it to the original is the concept of "prom night".
I mean, sure, Prom Night 3 was the only one to be a true sequel to the one before it (both featured the character Mary Lou), but Prom Night 4 was an entirely new story altogether.
So... calling it Prom Night 5 would have made more sense, since no one would see it as a remake and fans of the series wouldn't just assume that it's a direct sequel to any of the other entries.