Not that I disagree with your assessments in general, but the published depth specs are actually the right numbers to use when you are talking about rack shelves. The shelf doesn't need to extend out to the full depth including cabling - that would be a waste (and an inconvenience in many racks). EIA 19" racks are a bit of a different ballgame than entertainment centers and such.
Honestly I'm not sure a "space required" spec is really all that realistic. It could be misleading in many circumstances. Some cables that an individual owns may require more space to fit properly, so you'd still end up with confusion. At least when you see a depth spec, you know that it's the depth of the enclosure, and that you will need to add on several inches to that number to know the total depth required, depending on your particular cabling needs.
If you're trying to jam something like the 990 into a depth-confined cabinet, you have a lot of other issues to deal with. There is a *lot* of I/O on the back of the 990, and jamming it into some inaccessible, cramped cabinet is just asking for headaches. I can't even imagine how you'd work on your setup like that.
By the way, there are right angle XLR connectors (e.g.
http://www.audiogear.com/Neutrkcart.html ). I don't think they'd fit very well into the 990, however, since they're closely spaced.