I shoot MF and LF, so typical apertures are f/11-f/32, given how hard it is to focus at night. That means times of 30-1000s for ISO100ish films before reciprocity-failure correction. While it's possible to filter the C41 after the fact, it's NOT possible if one or more layers fail so much earlier than the others and end up entirely blank. While obviously one can't post-filter Velvia, if a C41 film had the same per-channel failures that Velvia has and you shot it at 1 minute without correction, there would be detail only in green while both the red and blue layers would be blank; no amount of post-filtering will bring back details not recorded in the neg.

Similar reasoning as to why people use blue filters when shooting under tungsten. Sure you can "just shoot" but unless you add two stops of exposure, your blue layer will be blank and no amount of filtering during printing will bring it back. Might as well shoot with the filter, wear the same 2-stop penalty and end up with a reasonably-balanced neg that won't max out the enlarger filtration.

I did some bracketing tests with Portra 160 the other night but they were just a matter of wandering around outside and taking some photos, certainly nothing controlled. I was hoping someone had done the controlled-experiment thing and posted a table of results...