It wasn’t said that it would “release”, but that it would become available. Considering that it’s currently in alpha right now that makes me think they’re going to allow people to purchase a way into the beta in probably limited runs so that it’s not 1 big wave of people flooding and crashing the servers, but more of a gradual ramp up to test them.
Also if they plan on making this game either launch through steam or an .exe on your desktop, it would only help the game in the long run to do that for the beta phase before a full release of the polished game. The only people that seem to get away with releasing an unfinished game are those making MMOs recently, then just adding the rest of the game through patches. Can’t say that I know Garrys work that well yet, but I doubt he’s going to make a move like that