[question] when has a map reached alpha/beta/rc state?

That sounds right to me, for me also beta should be the first round of detailing, minimal dev textures and what not. IMO it's something that you would be comfortable with letting people play on any server, not just reserved for testing.

Alpha is usually basic cubemaps, dev textures (unless major places need placeholder textures) and basic props that give an idea of what the final map will be like. This stage is mostly for major construction, gameplay and gamemode testing for changes (eg. changing cap times, moving spawns etc.)

Beta is mostly texturing, improved cubemaps, detailing and props. Construction is not done much here, but can be done for major things. This stage is mostly for detailing.

Releace Candidate is for maps ready for releasing, and need feedback based on gameplay changes done from Beta (eg. props affecting cap time and cover) and polishing off. This stage is mostly finishing up your lighting, HDR settings and final compilings, including minor bug fixes.

Final is what it says, the final released map.