People make 10 cm modules, and will continue to, and some people will make their extra PCBs and panels available, whether they’re “standard” or not.
What would be unfortunate is if there were two incompatible “tile” formats causing confusion and ill will, as is the case in Eurorack. Putting something about “tile” modules in the Kosmo Specification topic might help prevent that. But then again, it seems unlikely. The reason there are two “tile” formats in Eurorack is because of Eurorack’s confusing non-even vertical dimension. For Kosmo “tiles”, 10 cm is the obvious thing to do and I’d be surprised if there were any trend toward, say, 9.7 cm or 10.8 cm formats.
Anyway, “the Kosmo standard” is almost an oxymoron. My Kosmo modules have slotted mounting holes in disgard of the Kosmo Specification, and my panel component holes and pad sizes are a little different as well. It says gate signals are “minimum 4V, typical 5V?” but we’ve just had a big discussion over the Plexquencer’s 8.4 V gate threshold. Sam gives “2.5cm/5cm/10cm/20cm/40cm/60cm/80cm” as allowed widths but the Kosmo Specification just says “multiples of 2.5 cm” and I’ve made a number of 7.5 cm ones. People do what they want to, but it works.