My guess it that every year they just got crisper and crisper, after RTJsr's remodels and pretty soon, the crisper the edge the more perfect the maintenance was thought to be. It was probably the relentless march towards preceived perfection.
I would be interested to know if members hadn't seen the way MacKenzie bunkers look at greensides (not FWs) at MacKenzie's courses in Australia, particularly Royal Melbourne, and then thought that is how Mac's bunkers should look.