So after establishing that some of the range, including framesets, are in stock with Trek, it seems like finding a dealer with a small (15.5) in any model in stock to swing a leg over is proving tricky.
The standover looks big on the trek geo charts, but this could just be dependant on how / where they measure.
I don’t suppose anyone has any pictures at least of the small size (it’s for the Mrs who is 5’1″).

Not sure many will stock that size mind trek work in some odd ways now want a Factory shop remedy all sold out on pre-orders don’t know if they will order anymore mind they do have 2 15.5 in stock in Milton Keynes not much help to you.