Great idea - let's self impose rules on our team and then join a league without those rules, then call everyone who beats us a cheater even if we have no idea if they are or are not following the rules we made up. Fun.
No one self imposes rules not allowing holdbacks. The clubs that don't have holdbacks just didn't have any show up at tryouts or accept spots on the team. No club would tell an older kid, if they are better, that they can't play for them. Most of the lower level clubs have prefirst kids on them too. You just don't notice them because they aren't good enough to stand out. Looneys 2022 has a bunch, and they play in the B division.