Mike,
I'm not sure if you had a chance to look at the other post dealing with this question. Below is some information that I came up with while briefly looking into this. The AISC info was from looking over AISC 13th edition, table 1-1. I was just looking at the items described as shapes. Not the most technical way, but I could not find a definition. The A6 info came from A6-08 Terminology 3.1.2 Shapes (3.1.2.1 to 3.1.2.9)
I also have a copy of A992-98 that lists W shapes only. And as you have mentioned in 2000 lists only W shapes. The first edition I see the change is in the 2002 edition of A992. This lists "rolled steel shapes for use in building or bridges, or general structural purpose", the same as the current edition. It is odd that it references bridges, but bridge spec's do not use ASTM's only AASHTO spec's (another useless observation).
The spec (A992-06) is titled Standard specification for structural steel shapes.
AISC references W,HP, C, MC, WT, MT, ST, 2C, 2MC shapes (angle is not referenced as a shape)
A6 references W, HP, S, M, C, MC, and L shapes (L being angle)