No its not about getting it all on paper, you are making several assumptions, the colour separation decreases with exposure on the negative. Tones start to compress even at +1 stops, regardless of what you want to believe, you need to give it a go and analyse the actual negatives.
Extra exposure increases density, hence you get a thinner image on a denser negative. Minimum density increases faster than maximum does with increased exposure. This also causes increased graininess.
Your use of the word 'thinner' is making no sense in this context unless you are talking about the print getting thinner, less dense, because of the negative is more dense, thicker, and blocking more light in the enlarger.
What am I missing in your point?
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Ana´s Nin