Glad to hear the V2 bearing wasn't necessary. Suspect what the dealer meant by a "coating" on current bearings is actually an integrated plastic seal, which also functions as a spacer much like the old orange seals (and silver cap on older SRAM BBs).
Lest anyone get the wrong idea about your "fixed cup systems" reference, the distance between BB90 bearing cups is also fixed...there's just a different set of seals and /or spacers involved to take up the slack depending on what BB your crank requires. This is not unique to BB90 either. Which brings us to the wave washer...
In a quick search through the forum plus some googling it seems the wave washer should be treated as an "optional" item...or, more accurately, as an "if needed" item. Whether as-designed or due to tolerance stackups between frame, bearing, and crank manufacturers, you'll have situations where the wave washer is not only unnecessary, but actually could contribute to the very problem you note re: axial loading on a radial contact bearing. Several SC owners (and, notably, some other brand owners as well) have found that their GXP-based crank & BB combo has no axial play after everything is torqued to spec...
without the wave washer installed. Most often, this is discovered after an installation
including the wave washer where the cranks seem unreasonably draggy.
The above certainly jives with my experience installing GXP-based cranks into my various BB90 bikes over the last few years...I don't think I've needed a wave washer in any of them.
Side note: GXP crank install torque is substantial. I've sometimes referred to "getting my gorilla on" when installing them, so it's possible people (particularly if they don't use a torque wrench) could put a wave washer in there and only get things tight enough to where the cranks seem to spin freely without lateral play but in reality they've got a loose crank that is going to gradually walk around and make noise, damage the bearings, etc.
Good tip on the teflon tape. For a bunch of other really good BB install tips - for all standards - all in one place check this out:
http://www.vcrcbike.com/...bfiles/bbinstall.pdf . While it was compiled by an aftermarket bearing supplier and includes some info specific to their products, I found there was a lot of best practices info and other neat tips in there...like the tubular glue version of your teflon tape trick :-)
Cheers!
Carl Matson