Weeeeelll.... =)

Don't forget that if you have lots of grading and dissolves and effects, when you later on reconnect with your original footage, the computations will be made directly on that footage- in that codec and color space (4-2-0)

And that is probably the main reason for going intermediate: to avoid laying effects and grading on a delivery codec such as h.264.

Normally the proxys would be used as replacement for the chosen intermediate (422, 422 HQ... ) and NOT as a replacement for the original footage.

I think some even discard the original footage after converting to an intermediate and then call the intermediate the new Digital Master.