It certainly depends on the tactics the guides are using to catch fish. Having the extra rod does help produce fish obviously, but when freedrifting like the cowlitz, lewis, bigger rivers there are advantages of having the guide fishing rather than catching fish. When freedrifting you're as good as your guide because he is controlling everything. The presentation being the most important part. I know when I'm running the sled it helps to have a rod in my hand fishing because what my rod does everyone's rod does in the boat and if you couldn't actually "feel" what your baits are doing, your catch rate could drop a little. Feeling the angles, currents, speeds, all the factors to making the perfect drift everytime which results in fish to the boat.
But all in all, I'd leave it up to the client to choose whether or not he wanted the guide to fish. If the client is out to catch and release it doesn't really matter anyway. But for those that usually hire guides that just want to fight and land a fish I'd beleive they're happy to have the guide up the odds. Some people are just tough to teach, and when they pay the money they do it's easier to learn when you see what you are supposed to be doing..
Keith