Huh. I wonder if it's just a pressure thing. Looking at their chart, they seem pretty conservative on the wide rim front, as well - they don't even want their 30mm on a 23mm int width rim. I used to reference Enve's compatibly chart for the G23, since it has the same internal width, but I they don't seem to have a compatibility chart for that wheelset anymore.
I'd personally skip it, unless I found them really compelling vs other options.
Do they just pass along a personalized discount code? I assume, then, that you can go with any color you want, too? I haven't inquired in to a size-down, yet, but I'm probably going to soonish. A couple of weeks ago, I got an LS Pro Team Training jersey in M, and I'm liking the fit more than two SS versions that I have in L.
Oh, FWIW, I'm loving the LS PTTJ
. The front-facing panels of the SS version are really airy, but the LS version is still light enough for year-round use, I think. Since I wear sun sleeves all of the time, anyway, that's perfect for me.