^I never quite liked the manual, esp. where it tries to clear up these "areas of uncertainty". I argued elsewhere as to why the manual wasn't that trustworthy but well, without really going into that, the manual isn't very clear as to when the timeline actually "starts". It says that it's around 2001, but what does that mean really. Does it start in 2001. Or is it 98-03?. Whatever the case, 200X is still the "official" gantz time. How i read that was Oku saying "if it's that important to you, just say it was 2001, but I still reserve the right to change that whenever it suits my purposes". So yeah, I never put much money on the date figure.
But well, since you raised the issue, the manual was ~Tae Arc and that was what? 3 years ago now? Oku has had heaps of time to change his mind about how gantz should work, and things like the Maximum no. of points per mission wasn't clear until the very last chapter. Personally, I think it's high time we stopped putting up manual as the ultimate gantz reference. It's still a good place to start, no doubt about it, and, as far as I know, Oku hasn't actually gone against something written in the manual, but at the very least, I don't think it's as relevant today as it was when it just came out. Of course, that's just my opinion. I apologize to all manual diehards if you found this offensive in any way XD.