Glad to see you're paying attention!
Which is a face-saving way of saying "D'oh!"
I was thinking 320 was more recent, but can't cite anything. Interesting that Kodak claims 1954 as the introduction of 400, which is when it was brought out in 135/120, considering that Tri-X the film came out in about 1939/1940, though just in sheet form, as I understand it. So I suppose 320 being the Tri-X in sheet form these days, it could claim descendency from the original.
Anyway, don't attach much to the word "Professional". Remember that the Elitechromes were listed on the Kodak website as consumer films, but they were called Kodak Professional Elitechrome 100, 200, and Extra Color 100.
Also, the 400TX box says Professional on it.