The fronts on all except the Cub LoBoy have worn much faster than the rears and I don't believe grooving had much to do with it. I blame it on other things:
Most of all, the (what I think is) excessive positive camber runs the load on the outer edges of the tires.
Then the scrubbing when turning in 4WD doesn't do them any good. Whatever difference in travel needs compensated for that can't be made up with drivetrain slip does happen somewhere. If one or more tires can't slip, something expensive and metal will break. Although many believe that it's fine to put the tractor in 4WD the day it's delivered and leave it that way forever - I don't.
Then it's the common sense that the fronts get a lot more "miles" on them that the rears. They might rotate twice or more as much as the rears. My tractor gets run on the road into town for snow removal and to help with various projects. That can a round trip of 3 miles or 6 miles depending whether it's for the church or the gun club. Those trips are made with the FEL or heavier 8' plow on the front. The road guys here do a great job of spreading "car dissolver" here, so the roads are often only wet when there are parking lots to clear in town..
The first picture below is from January of 2019 when the tires were grooved on the 977 hour new-to-me
L4240. I don't have record of the hours when the next two pictures from January of 2024 were taken when they were regrooved. Probably around 1400 hours. This shows how much camber it has. The insides were barely worn in 5 years.
EDIT TO ADD: The these tires have 1600 hours on them and they look like they'll last for a while longer.