Use what feels best. Way back when I ran minimalist "road" saddles(SLR aka ass hatchets) on my cross and MTB because they were easy to slide around on.

However, there are such things as MTB-specific saddles, like WTB's High Tail. It's is great on my MTB (the rear is cut out to prevent tire buzz at full compression). That cut out serves no purpose on my gravel bike so I stuck with a tried-and-true Silverado instead.