Being on this board, there are a variety of opinions on mustang rolls, bevels and all that stuff. No one is wrong. Some like the bigazz bevel, others like a minimum bevel. Some like the water line carrying the weight, some don't go that far. There's 2 sides to flares , too. Some like to rasp them flat, and some leave them mostly alone except getting the flared wall off the ground to prevent more flare.
I don't think anyone's wrong or right. Wait.....I think everyone is right. We all want the same things and eventually we all get there.
My soon to be ex farrier does not believe in backing up the toes. He doesn't bevel either. I leave it alone because my horse chips away her long toe all by herself. Hopefully it annoys the farrier.
I think the point in the 'mustang roll' is to get the hoof to look like this one or this is what I try to mimic when I do a roll.. when you roll the hoof its more to ballance the hoof- keep flares and cracking from happening- and to take out the sharp edges the nippers leave behind.
I never rasp more than that (to bevel).. not sayin its 'wrong' I do believe it takes away the hooves ability to retain moisture when you rasp too high up on the hoof wall though.