I think I get your point, but to me sidemount skills should be considered foundational skills — they apply in every use case, and instruction shouldn’t be equipment or environment specific.Tulum Mexico has some of the finest X Deep instructors but that won't help you diving a Halcyon in some cold quarry in Oregon.
After demonstrating the required competencies, a SM diver should only need a 10 min familiarization discussion to be capable of using the vast majority of SM equipment (know your inflates, dumps, redundant lift).
The only thing that varies for me between 2C and 26C (from rash guard to drysuit) from a sidemount perspective is my backup up buoyancy (if I’m bothering) and maybe my tank attachment point if I’m switching from steel to AL.