Hi, I'm new here. I'm from Argentina, home of the Blue Meanies, sorry for my english.
I love this kind of discussion!!!
I'd like to give my experience in this theme. I'm a "George" in a Beatles Tribute Band and a George Tribute Band.
It's true that the George's parts on the harmonies are very low in the mixes and were really rare and hard to sing. The example of "I'll get you" is good. But this no mean that George Martin hide his voice in the mix, remember that in 1963 the Beatles recorded "live" in the studio. Probably the 3 sang in 1 mic and the John and Paul voices were strongest that George's.
"Because" is other with a very difficult part 'cos the George's part is the less evident.
One more time, sorry if I make a mistake, tell me and I try to correct it.