i guess it's so they can have a horizontal top tube while maintaining reasonable standover?
i've got a quite big stack of spacers under the stem on mine...as have most of the other builds i've seen.
i guess it gives the option for maximum slammage though?!
2019 kepler disc https://www.brothercycles.com/2019/02/the-2019-kepler-disc-first-look/
they've done away with a rim brake option for 2019