My theory is that if they are not resilient enough to handle the scraping they will be self trimming. But there are two advantages of leaving them as is.I just could not stand the scraping sound. I pulled them off today and cut off 1/2 an inch and much less scraping. Perhaps it is just me but not sure a well designed Mud Flap should be scraping regularly while driving.
The first is obvious - the longer they are the more coverage they give you in terms of blocking debris…
The second one is that they warn you that this might be a good place to set your suspension to high in the future.
I’ve had warnings like this before but it is from the bottom of the car hitting the curb cut out… So this is somewhat of a pre-warning