I think the more significant detail about "keyboards with reduced number of keys" is instead "keyboards with multiple thumbkeys".

On a standard keyboard, your thumbs only get to use spacebar. With these small keyboards, my thumbs get to use space, backspace, enter, escape, tab, delete. (And I put the modifier keys as Home Row modifiers).

Albeit, this is almost entirely orthogonal to how the alphabetical keys are arranged. Having 2-3 keys per thumb would be a benefit to any keyboard; where the main downside is "keyboards with 2-3 keys per thumb are expensive or diy".