Yes, you are right, I shouldn't have tried to put it that all into 'one word'.
1. Equipment skills. Set-up, adjustment, familiarity, operation, function etc..
All completely different in sidemount config, including SMB use, etc...
2. Emergency/contingency skills. Air-sharing, CESA, Cramp release self-rescue etc..
All different or probably even not needed anymore. I would not teach CESA in a sidemount class.
3. Personal skills. Propulsion, breathing, stability, control, compensation etc..
All different or at least much more complicated and advanced
4. Non-technical skills. Communication, team work, situational awareness etc..
Partially different. Since focus is more on self reliance, probably very different.
5. Psychological skills. Stress management, focus, discipline etc..
In my opinion: easier in sidemount. Greater feeling of control, less stress.
Totally different because of that.
6. Operational skills. Dive planning, run-time management, ascent protocols etc
More complex gas management, and different in other ways as well.
7. Mission skills. Specific to the specialist area, if applicable; guideline use, DSMBs, liftbags etc.
As said above, SMB transport and use is already different, liftbags are carried by many for redundant buoyancy, requiring good training and skill to use them fast enough - or the knowledge that it does not work for you anyway,
guidelines... man did I have trouble when I always refused to keep my hand on the line on decends and accents in Egypt...
Use of lines for overhead is not taught actively by many instructors to keep the students out of there and within 'rec diver conditions'.
Equipment skills are just the tip of the iceberg. But they are nonetheless important and part of a very holistic necessity.
Equipment influences most skills and the way to teach and learn them correctly and efficiently.
As you can see above.