First off breeder times are super loose guidelines and you should not put much weight in them. Those times are for that breeders garden and plant not your garden and plants.
Secondly "flowering time" as stated begins when the plants begin to form flowers. Some breeders will state 12/12 time instead. However flowering time begin when you see flowers.
Every plant is different so counting from 12/12 is totally arbitrary and is only done by stoners growing indoors.
If you were growing outside you wouldn't say your plant was flowering until it started growing flowers. So why would you play make believe inside and say it's flowering before it starts to show flowers? It's very basic plant biology. There is a transition period between veg and flower. Many nutrient companies even identify this stage on their feed charts
. If you look up the stages of plant growth there is usually 5, and this "transition" phase is commonly refered to as the " preflowering" stage. The plant wouldn't enter the flowering stage until it starts making flower
.
Hope that helps. It's a hugely common misconception with new growers especially, but with many online cannabis growers. The more you understand about the biology the less sense it makes to count all plants from the arbitrary 12/12.
Just because we grow indoors does not make us gods. The plants still have to do their thing in a certain genetic order.
Personally I've come to believe that we can not really speed that genetic timeline up, at least not much(but we can totally slow it down). I think our goal is to provide the most ideal conditions to facilitate the natural order of the growth so that it can happen as fast as the plant is genetically capable of.