If you mean horizontal top tube mountain bikes, yup, pretty much, sorta like road bike sizing. At least in crotchal clearance.

Last year I snagged an early '90s rigid mountain bike, horizontal top tube, 58cm frame. Univega Via Carisma, pretty much their early concept of a hybrid, minus the serious off-pavement wheels and stuff they put on their Alpina with pretty much the same frame. Technically my size, but if I'd intended to do any serious single track or downhill, well... first of all, I wouldn't because I'm too old and haz no skilz. But a 56, maybe even a 54, would have been better for that, mostly to protect to boys in the event of unplanned forward dismount.

The top tube is probably a bit longer than a typical 58cm road bike frame of that era. Combined with the original flat bar it was darned uncomfortable for me, at least last year when I was still trying to get back into shape. Hurt my neck trying to ride more than a few miles.

I swapped the 2" riser bar from another bike, which put the height and reach right where I needed for my rides on pavement, gravel, etc. It's basically like a current model sporty hybrid -- feels pretty much like a flat bar Trek 8.something FX I test rode last year.

I've considered putting on some lower all purpose drop bars, but I'd probably need to replace the stem as well. We'll see. A couple of riding buddies like the mustache bars they put on their rigid mountain bikes for gravel rides. Gets them a bit lower when needed, with enough flare in the drops to retain plenty of room for manuvering.