First 2 weeks in flower

Ok, you always see people asking how much longer their plants are going to take and how many days in flower they are. But something that confuses me is when do you start counting how many days they are in flower from?
I've heard that the first two weeks after you switch it to 12/12 don't count as flowering because the plant is still making the transition from veg to flower. I don't know if this is true or not, but it seems to work good for me. In the past, I've tried counting right from when you switch the lights, and I've found that it's too early.
I realize that the finishing times that breeders give you for certain strains are only guidelines and that you should go by trich clarity (or opacity as the case may be), but i think a lot of growers (especially new growers) are cutting their times too short by counting from the minute you change the lights over.
Am i wrong?

I would get into this but it's a touchy subject here....I think it goes by whatever you are going by...everyone has there own opinion on this one...I just go by when they are done...you can tell when a plant is done, and it is rarely when the seed company says they will be done..it's nature, and its not perfect...