Just because SH has special powers over ppl sworn to the shadow, doesn't mean that his OP limiting ability is limited to shadow-sworn channelers. One doesn't automatically lead to the other. You can speculate all you want, but it is still just speculation. We have no idea that he can't limit OP access to "light sided" channelers. All we do know for certain is that he can limit access to the OP.
Here is what we know:
He has some difficulty in 'real world' manipulation, ie he needed Elza's help in freeing up the Domination Band
He can "mark" people a la Alviarin
He is tied to SG, and at least earlier in the series, had to return there from time to time.
He can limit access to the OP, nullifying it in some way.
His "real world" limitations don't affect his ability to rape.
Unlike all other Myrddraal, he doesn't have to obey the Forsaken
At times, he seems to be an avatar for the DO (but not always)
Unlike other Myrddraal, he has a sense of humor.

Any other conjectures are just that, conjectures.

NaCl(still not enough information to make the assertions you do)H2O