This is hyperbole. Latitude is something that you can measure, and Tri-X does not have "stupendous" latitude. Tri-X does have better latitude than some films, but if you want latitude, TMAX has more. Tri-X does have nice grain, but the grain is very fine...if you want course grain, there are better films for that, and if you want fine grain, there are better films for that. I find that Tri-X is a rather ordinary film. A high-quality film, but not a film with any special qualities. So it's silly to say there's no other film that can do what Tri-X does because it's just not that special.
On the other hand, there really aren't any films that can do what TMAX400 does. Tri-X can be substituted with any number other films with similar qualities, but if you are using TMAX400 for the fine grain, high speed, good sharpness, extreme latitude, and low reciprocity failure that it provides, there's not anything else that really falls on the map in the same place. Delta400 is comparable but not quite as good, in my opinion.
TMAX400 is truely the "Have your cake and eat it too" film. If I had to standardize on a single film, it would have to be TMAX400. The combination of speed, grain, latitude, and sharpness make it the standout choice in everything from my Pen-F to 4x5. If I have one gripe, it's that it's slightly expensive and fixing it is really annoying.
TMAX 100 is also phenomenal but a little less special; I think that Delta 100 and Acros are fine substitutes for TMAX100 in most situations.