The point is, you're mixing two different words (stable & official) for no reason. 1.10 is also an official release, because it's derived from AMXX's own community.
I guess it depends on how you think those words are defined. IMO, neither 1.9.x or 1.10.x have been "released" in the context of a basic end user. But again, it depends on how you define "release" and what context surrounds it.
For example, some software companies use the terms "pre-release" or "release candidate" to indicate that something is not yet the official version but it will be if testing goes well. This implies that a "release" is the official stable version (again, usually in the context of the basic end user).