funny thing, i mostly just want to know how old. mostly because i "judge" my plant based on that. its my first grow though, i am sure that will change. it is just that with each person calling it what they want, it makes things less than ideal for a learning purpose. or even a doctoring purpose. and especially on a science purpose. if you each call something as you please, then each time the "age" or "stage" comes up, we have to have 3 pages of "but i call it this, and i have been calling it that since dirt was discovered. but the lack of formal definition causes more harm than good.
the veg stage starting when it pops is the least helpful to the most people, also, that method does not line up with the breeders time lines. the flower starts at flip, is less helpful too, and again, the breeders timelines match up much better with flower starts after you see the flower parts.
it will take a long time, but with things going as they are, the legalization of the plant will help with things, especially the science.
i agree that people should do what they want in growing it, and sadly that just leaves reading those three pages and figuring out what each person means by what they say.
things like changing humidity or light height or temp for the needs of the stage of the plant are much more difficult to ask than they need to be though!
if a plant grows outside, far from your home and you discover it, then you dont ask mother earth "have you flipped yet? you look and see if there are any pistils, if yes you call it flowering, if not you dont. but inside a home that changes? that alone does not make sense. your eyes tell you when it is flowering, but in the other case, you have to find a person to tell you when it was flipped, your eyes are dont count at all.
then... what about autos? you do not flip, but you watch and see the pistils. so that method, the find out what day it was flipped then calculating, isnt even consistent for one farmer who grows both auto and photo. the same farmer who would base things on the flip for photo wont call the auto flowering till they see those pistils.