Oh, then I probably just got you wrong. Sorry.
Which maps do you think of particularly that were good but not added because of not being "acknowledged" by Mapcore?
Yes, there are a couple of maps that looked interesting but never got added (Grind, Import, Sanchez, Waterfall, Iris, ...). (Just talking about the visuals, not layout, because that's obviously Valve's first exclusion criterion)
But maybe there are different reasons. As I already said, they might just have failed when tested by Valve...
Or maybe there were just other maps that were better at the same time.