I've built a Planck (40% ortho) and I can say for sure that I personally don't find the short finger travel between keys to be worth having to hit two keys to type a number, for example. Instead of moving one finger an extra row to type a number, I now have to move two fingers.
The problem here is not the lack of an additional row of number keys, but the poor other choices in physical keyboard layout (based on largely following the historical pattern of a 19th century typewriter design; in the “planck” example with an arbitrary ergonomically-useless horizontal shifting of the rows). It also doesn’t work very well to put the numbers on a shifted layer but all on the same row, requiring 8 fin…
Number keys are also indispensable for games where you need to switch items while moving. A finger or two are already going to be busy with the motion keys, adding two more fingers that don't overlap with the motions is going for some octopus keyhandling.