It should be a major concern when a league puts out a Sport shot without actually certifying as a Sport league. That allows bowlers to establish a certified average less than their THS ability without actually sandbagging, and that would certainly allow some bowlers a big advantage in handicap competition, especially if they bowl only in such a league.
i am in 1 of those leagues your reference, (well technically, not all the patterns are sport compliant) So, its a challenge league, its for people who want to get better.
typically, we have a short,medium and long pattern and then NATS
teaches you to play different parts of the lane.
i would say that most of us bowl another night or more and have a higher THS average
i haven't heard of anyone in that league over the course of 4 years ever mention that.
And its listed on bowl.com as a challenge league
i reported my challenge league average to my state tournament officials and they looked at me funny, they said, "whats your last years high average?"
I bowl scratch anyways, so it was a moot point