I call it Metolal. I haven't tried it with Tmax films, but I would take your word for it. My experience with HP-5+ and FP-4+ is probably giving about the same relative results. My test scene is a bookshelf illuminated by a picture window with a lace curtain on one side, so has a wide brightness range. I find that Metolal gives lower contrast than Rodinal. If I develop in Rodinal to get that contrast, I lose shadow speed. I really like it with FP-4+.
I also found I could double the concentration of the stock solution. It's pretty hard sometimes to measure as it is when I want to use an 8 oz tank on 35 mm, so the best I can say about more concentration is that it's the way to go if you want to store lots of it.