I love the idea of these but have never experienced a situation where a regular TKL keyboard is too big for a desk.
If I need something smaller, chances are I'll be using a tiny little folding BT keyboard rather than something non-folding with full-sized keycaps.
I guess I just can't see myself ever wanting to relearn a keyboard layout to drop from 80% (TKL) to 60-65% layouts like these. I'm not even keen on the 75% TKL layout that smushes keys together just to save a fraction of space.
I would even consider myself a potential target for this niche market as I often SSH into a headless bank of rack servers from a tablet and want a keyboard better than the on-screen one. I just can't see how the 60-65% is enough of a reduction over the 75-80% models to justify taking it instead of either a normal layout keyboard, or something that either folds into a jeans pocket, or folds up against a tablet.