Bernard,
Getting separation in the shadow values from a film with a long toe (e.g., 320Tri-X) has nothing to do with how you expose the print. If you want more shadow separation from a long-toe film, you need to give the film more exposure, moving the shadow values up off of the toe and onto the straight-line portion of the film's response curve. Most modern films do fine with a stop or a bit more of overexposure. I overexpose intentionally fairly regularly with 4x5 320Tri-X just for that purpose.
If you give your paper less exposure in order to get more separation in the "shadow values," then you just end up with a print without any real blacks in it. Fine, if that's what you like, but I like a real, tangible, black in most of my prints. Even with short-toe films, if you really want a deep black in the final print, you'll need to expose the negative generously enough so that you can get the detail and tonality in the darkest areas that you want while still having a dark black for the areas of the negative that are close to fb+f density.
Now, when we let mid-tones be our guide to choosing a print contrast setting, that doesn't mean that shadows have to print darker than we'd like. We just need to dodge/burn accordingly to get the result we want. If the shadow separation is there on the film, then you can get it to print at any contrast setting. The trick is getting everything together in one print in the tonal relationships we want. Sometimes it's eminently doable, sometimes we have to make compromises and sacrifice a little mid-tone separation in order to get the shadows and high values where we want them.
Bottom line, you need to expose your shadows so that they print with the tonality and separation you desire while at the same time giving you the deep blacks you want for the darkest areas of the image. Just giving the paper less exposure to get detail in the shadows can result in less-than-black blacks.
Best,
Doremus