The 90mm was mainly to make sure that no one on the start line has to measure a wheel (as there's basically nothing on the market deeper than that apart from niche wheels like our TITAN (100mm), a Flo 9 (95mm) or a Knight Composites 95mm), and I wouldn't expect anyone to try and ride them.
Otherwise you might get people using 82mm Zipp 808s (which are road race/crit legal) and others not noticing until later, cue lots of anguish etc. plus the raft of 80-88mm wheels which get used in RRs and crits. The more restrictions the less people enter, that's our thinking.
The CTT outright stole our rules for their classic series events and have basically kept everything apart from changing it to 65mm which is a weird non depth.