If you are relying on the breeder's time frame, don't. Use it as a general bit of information, not canon. Just like the height, weight, and THC percent they give. The plant will tell you when it is ready.
For example, I've had 4 plants of the same strain go ginger 3 weeks apart. If you grow this strain again, you might hit the 9-week mark, or maybe even 8.