bit fit should be based on the top tube length and the reach etc of the rider, not the seat tube length. Seat tube length is irrelevant to the fit of the bicycle. When I see him on the Large bike I see him cramped with respect to the reach going forward. 25mm in the top tube is a lot of difference (for most manufacturers when you jump to the next frame size, say from a 56 to 58, the top tube jumps 10mm), and would be the difference between a bike that would fit confortable and that would not.

If it were me and my money on the line, I would go try the XL and see you can make that work.