I still don't get this thought process. Why in the world would Apple send out buggy software to be tested every 2-3 weeks and deal with millions of feedback reports to wade through regarding issues they have already fixed if they already have the final version? Sorry but that just makes no since.
I do agree they have newer builds internally than what gets released in those weeks but certainly not a final GM already. More likely newer daily builds to be released at 2-3 week intervals to the developer community.