W.r.t. a 24" bike wheel where one of the folded dimensions is 23", their FAQ says:

"Many different tires sizes can fit on the same rim. For example, in our case we use a 1.5" wide tire on a ERTRO 507 rim (approx 20"), which brings the overall diameter to about 23". If we used a wider tire, such as a 2.25", the diameter would increase even more. To try and keep things simple, the bicycle industry calls it a 24" wheel. For more information on bicycle industry tire sizing please visit: http://sheldonbrown.com/tire-sizing.html"

I guess that is sort of fair --- if also sort of tricky (intentional or not). But again, if you look at the picture of the bike folded, even if you took the seat out it doesn't look to me that you can fairly measure any dimension at 23", assuming their total (inflated) wheel diameter is 23".

Maybe I'm going overboard on this one, but I far prefer that when I look at stuff like this online that I can have a sense that I can really trust their data.

I hope lots of people buy these and write up impartial reviews because it IS very interesting. Wouldn't want to be one of the first ones, personally. But who knows, maybe in a couple of years I'll end up buying one and be a passionate supporter.