I would be curious to know if the small wheel recumbent market has grown
enough to make the introduction of these tires feasible, or if the sales
of small wheel upright folders are creating the demand

Good question, Tom...
In the 4.5 years that I have been bent, the amount of tires available has
grown exponentially. My wife rides an EZ-1 with Schwalbe Marathons front and
rear, I am happy due to my weekends are for riding and not fixing flats. The
stock Kwests were lethal in gravel or grass but flatted very well.

John H
N TX