Ive never heard alpha ever being used as a "gimmick" in the games industry. Its a standard. Alpha usually means the game can be played through from start to finish. This can mean start to finish with missing art, weapons, enemies, just about anything, but can be played though. After alpha there is still lots to do in art dev and design still. Once you hit beta, that usually means content complete, but any game dev will tell you content is always getting thrown in.
After beta is when the bugs start rolling in.
These are real terms used by every game studio in the world and used internally. Marketing has nothing to do with it.
Alpha in mp games or mp modes is usually set out with per game goals as multi-player is a grey area when it comes to "play through it all the way" Most game dev's will set out milestones for multiplayer rather then pass an alpha. once they feel its good enough to start playtesting on a large scale, you might call that beta.