Yikes 2 grands seems higher than what I expected...
What seems off about the Medium size in particular that you noticed if you don't mind me asking?
for some reason the medium frame does not share some common dimensions (chainstays are shorter (403mm vs 408mm on others), which results in reduced tire clearance (28mm vs 32mm), bb sits lower (271mm vs 273mm)). additionaly stack is only marginally higher than on the small version, but 40mm lower than on the large one.
i think that winspace only produced medium sized frames for initial testing, adjusted some things, but did not redo the molds, only made the adjusted ones for the other sizes