The Colt AR-15 was specifically mentioned by name. But, if you look nobody makes AR-15s anymore. You will find LAR-15, XM-15, etc...but no more AR-15s. In fact, if Colt ever places the model AR-15 on any receiver, it is automatically an AW regardless of features.
The ATF has allowed Post-Ban ARs. There are 2 reasons for this:
1) Series bans have been struck down in Federal Court as unconstitutionally vague.
2) A Post-Ban is not a duplicate of the AR-15 as it doesn't have a bayonet lug, flash suppressor, etc...An old article I saw in 1994 said something along the lines of the congress meaning having the same features by duplicate. So, an AR-15 type with Bayonet Lug and Flash Suppressor would be a duplicate of the Colt ar-15, But would also meet the feature definiton.