Drew already schooled you on this, but to address your example:
Judo doesn't require better technique than Greco, but if you were to employ a pummeling-based Greco bodylock game in judo, it would require a higher level of (offensive) pummeling skill than if trying to execute the same game in a leotard.
Similarly, pulling off judo style foot sweeps at arm's length in (freestyle) wrestling is more challenging than in judo, since the lack of gi grips makes off-balancing someone at that range (e.g. using collar-tie & wrist control) a lot harder.
i understand what you are saying, but i don't agree with the example you use.
the body lock is my best takedown, i do it all the time, but in the gi guys just grab my collar or the sleeve and create distance, so no bodylock.
it is true it's harder doing the bodylock in the gi, but it doesn't mean i am not proficient at it, the move work in the gi as good as in nogi, but it require a completely different skill to get in position, the judo grip fighting and my judo game is non existent.
actually to learn a new move a person should drill the move with less "hindrances" as possible, usually with a non resisting partner.
after he learned the technique, he can try to catch people during rolling, but i don't agree with using a technique against all odds just to get better.
try to use the RNC in the gi is harder and it is not smart, the bow and arrow choke is much higher percentage.
trying to force the RNC in the gi is not making your RNC better in my opinion.
the same with the guillotine and the darce, if you can guillotine and darce a lot of guys in the gi, good for you, you have world class chokes, but it doesn't mean a guy that want to get good at guillotine and darce should try those moves in the gi a lot.
most of the times (non collar) chokes are harder in the gi because of friction and the opponent can grab some part of your gi to slow you down.
i remember watching a video of Marcelo explaining that speed is everything in getting the tap with the guillotine, that's why he use the classic hand clasp instead of other stronger hand clasp, because it is faster.