I agree with both Captain PB and 4dogs (excellent post, by the way).
Actually, when I hand fly an ILS (not very often, I'm afraid) I usually maintain flight path one way (like the AP/FD A/TRH) as well the other way, instinctively, depending on circumstances. My body and my brain know what is required and when, so I just coordinate the two inputs (power and attitude) to achieve the desired performance (on glidepath, on speed) as necessary.
I guess we all do that. It is difficult to explain, so we set a simplifying rule. Or two. And then, we have something to discuss about.
cheers