I think one scene from KoD kind of disproves what you are suggesting. Nynaeve notices mixed links that are channeling giant balls of fire to burn Trollocs. She states that the intensity of the flames was too high for it to be from saidar (that she can see) alone. The implication is that saidin was used as well.

Now, if what you say is true, Nynaeve would not have said "saidar alone". Why imply the presence of another power if the link can enhance saidar? Why not say "unenhanced saidar"?

I agree with you on one thing, though. While each channeler in a link will be channeling a small amount of the Power at least, the leader can make them use different amounts, and not use any of their power at all if they so choose.