At 6-1 you almost for sure dont need a 22" frame with level top tube.
I am 6'5 and have a 22" frame with a very slight sloped top tube and its plenty big.

Mountain bikes should have more crotch clearance than road bikes. Easier to dismount during a short climb you cant complete or anything else where you need to get a foot down orndismount quickly.
This smaller frame is offset with s top tube which will be long for the frane size when compared to level tube road bikes.

Also, mountain bikes have a higher bottom bracket. This means you are starting out higher up vs a road bike.
Seat posts are now 350-400mm for a reason- mountain bike sizing means more exposed seatpost compared to traditional road bike geometry.