I also heard that TXP was designed to be retouched, having a special base or something. Being a youth, I don't even know what film retouching is or how it's done, but that's what I heard.
TXP, as said, is primarily a studio/portrait film. It is often used elsewhere with great success, but that's another story. Let's suppose you did a portrait of a person who has facial defects; scars, acne, mole, etc. A retoucher "paints" it away with dyes and a brush. TXP has a rough base so the dye will stick better. Now it's done with a mouse.
I've been using TXP 320 in 220 rolls for a while, rated 200 ASA, developed in D76 1:1... and TX 400 in 35mm rolls, rated 320 ASA and developed in D76 1:1... in my experience TXP has less fog and wider tonal range... TXP is hard to find, I have to special order it.
I would think there should be no fog on TX or TXP unless there are light leaks in the camera or developing tank. Assuming that the film is loaded into developing tanks in total darkness. Age fog would be a problem only with out of date film. Someone correct me if I'm wrong on this.