If the game currently crashes every hour on the hour, that is lots of time to show a couple people the game, but I don't think many backers would want to actually play it in that state. Similarly, there could be unfinished cutscenes or quests that would cause problems if you explored in a certain direction or talked to a certain NPC, which would be easily avoidable with someone there to give a warning, but less avoidable for all the people who don't read release notes.
More likely the finishing touches are being done, or there is a release candidate going through QA to make sure there are no obvious / serious issues remaining. And of course as Stabbey said, even if the alpha itself was ready to go it wouldn't make sense to release it to get feedback if the mechanism for receiving that feedback isn't done.
