Originally Posted by
Aeroplane
As far as the MTB wheels: I would bet that those MTB wheelsets all have 20mm front hubs, which don't have axles (the axles for 20mm hubs are proprietary to the fork). Also, disc rims are usually lighter than rim-brake rims too, since they don't need a braking surface. Tubeless rims are even heavier than those too.
None of the wheels I listed have a 20 mm front hub and all of them are for tubeless. The Crosstrail is for rim brakes.