You totally misunderstand. When 10240 was released in 2015. Insiders got it on 15 July. Public got it on 29 July. 2 weeks later. So when Win 10 Anniversary Update is released in July/Aug to Public, Insiders could get the final build by as much as 2 weeks before the Public.
Can someone else try to explain it to him how Insiders could get the Win 10 Anniversary Update by as much as 2 weeks before the Public does.
I dare say insiders will get it early, that way there can be final testing of the intended release build and a patch made if required. It would be bad if hey release it and there happens to be a bug introduced in the release build.
That also was the situation at the moment of the release of 10240, insiders got it 2 weeks early, then the general public got the same build and a zero-day-patch