I believe it's time for Andy (or anyone with administrative privilege) to set up a separate section for HL2 maps. Otherwise, it would be quite confusing to figure out whether it's a Source map or the original HL.
I think it'll just be a matter of time before HL2 maps start to flood the vault, so it should be implemented very soon.
Of course, the author can always denote the type of map in the map description, but not everyone would be that responsible.