Just haven't had the time to re-playtest the stand-alone build.
Let us do that for you. 
He's testing it so that everything is perfect- no bugs, no crashes, no way someone in the first 24 hours could hack the save file- just trying to cover all the bases.
Imagine if a gaming company did this - They 'completed' the game, but didn't have the resources to go through and check to see if there were any game-crippling bugs to sort out. So they release the game, people find out that there IS a game-crippling bug, and everyone is upset, they pull the rest of the copies off the shelf, they give free fixed games to those who bought the bad version on top of another free game- a huge loss of money, sure, but also damaging the company's reputation.
Man, it would be horrible if a gaming company this day and age ever pulled a stunt like th-*COUGHCOUGH*CODEMASTERS*COUGH*BUBBLEBOBBLEREVOLUTIONDS*COUGHCOUGH*
Yes, this game is free, but the point is that this is the version that will be the first 'full' version that he's releasing of it, so he wants everything to go perfectly, and you can't rush perfection *SLIPS TIJIT $100AU*