tl;dr the crankset is pretty unique and has to use the supplied rings

I was just looking at the tech volume.

The crank arms are the same between the double and single versions. The bash guard and chain ring(s) are stacked and bolted on the back side of the spider. The spacing of the double is created by dishing the rings. There are two BCD's. One with smaller bolts goes through the single or outer ring and the bash guard, the other goes through the single or both rings with normal sized chain ring bolts. All this is pretty unusual. It should be pretty strong, due to more and firmer attachment points for everything, but it means that a "standard" chain ring isn't really going to work, even with the same BCD; and so there are only the two options for ring sizes (42, or 46/32). It also means it's possible to strip the blind threaded holes in the crank, where a normal crank would just have through-holes and be in no such danger. The single ring is not narrow-wide.