They won’t go after a broker unless that broker is renting their own points to a degree that turns those memberships they own into a commercial enterprise.
They are not going to decide that an owner is violating the commercial purpose clause simply because they use a broker.
It will always come down to the volume of rentals an owner is doing that shifts them from renting within the rules, and their legal right, and renting to a degree and pattern that
DVC considers is an owner who is in it for a commercial purpose.
Any owner who rents a few reservations, even if it is every year, and through a broker, is not going to be considered an owner who has shifted into the commercial purpose realm.