What are the limits on dye-subs for group buys?

[Suds]

I go look at some of the pre-made sets, and I see things like this:

https://usa.banggood.com/127-Keys-Cherry-Blossom-Keycap-Set-OEM-Profile-PBT-Five-sided-Sublimation-Keycaps-for-Mechanical-Keyboard-p-1607889.html?cur_warehouse=USA&rmmds=buy

or this:

https://en.akkogear.com/product/year-of-the-ox-3068v2-rgb-mechanical-keyboard/

or, most especially, this: (warning: porn)

https://www.aliexpress.com/item/1005001848876409.html?spm=a2g0o.store_pc_groupList.8148356.35.594c72cdIHopBR

All three of these sets have full color printing on five sides of the keys, with pretty good definition. That porn set in particular is just full of color, every key different, printing on all sides, thick pbt, for $28.

So my questions are these: Who is making these keycaps? Gliging? If I contact them with my great keycap ideas, could I talk them into running a group buy?

That aside, what are the actual limitations of what is possible to print? I haven't seen a single group buy with printing anywhere but on the tops of the keycaps, except for a little on some of the spacebars in Space Dust. Very limited though. By all means correct me if I'm mistaken here, but it would be nice to know what is possible and what isn't.