I think this problem is entirely caused by golf association course raters... that and the fact that the GHIN system is a mess anyway.
The raters don't assign enough variation in overall course rating and slope between courses, so people who play easy courses are getting too few strokes, and people who play very hard courses are getting too many.
According to the guy who invented the system, a "standard course" had a slope of 112, and according to an aritcle in Golf Digest a few years ago the average was 118.5.
Regardless, I see damned few courses with slopes that low, and with a max of 155, there simply isn't enough differentiation between courses to account for how golfers actually play them.
When you add the fact that the GHIN system ignores one of the primary skills in golf--the ability to play well when you want to the most--we have system that doesn't work for most people.
Anyone who plays a course with lots of penalty strokes available in the form of water, OB or tall grass is, in my view, going to have a big advantage over those who play courses without all those penalty opportunities. And until the slope and rating system accurately predicts scores for golfers with 10-25 handicaps, the inequity will always exist.
I do put some blame on course owners and members, who don't want their courses to have a rating of 68 with a slope of 105, but that's about the only rational solution.
FWIW, I wish the slope number had been less of a public deal, and instead we had published the bogey rating, wihch is what the slope is derived from anyway. Maybe people would better understand how the system works.
K