Well there's one thing you know GG, that RIU is a cool place to learn things. So that's a start, lol.
Okay, so I do like shiney toys and I am probalby a fairly average bloke trying to be a new man but failing in a lot of departments, but when it comes to my weed I can be a bit cavemanish, or rather basic, I don't own a PH/EC meter, I don't do a lot of things people say is necessary, but hey, I like my weed just fine the way it comes out.
I think with diagrams like the one you posted, it's all a bit to, black and white. The diagram itself is basically correct, but people take things at face value and you got everyone getting all antsy and chopping at week 7 (and you know they are not waiting until the end of week 7 cause they want to get their hands on the goodies) subsequently they loose the last burst of growth, as shown in Ambers plants and she will benefit from her patience. Or they are growing a 12 week sativa and wonder why they can't get fat sativa buds like they see in High Times.
Now I like to be as organic as possible with growing, and take the same view with MJ plants and genetics. When you are looking at a sativa dominant strain within a hybrid, and you have a pheno that is say growing to a 12 week flowering regime, but even at 12 weeks there are mainly a mix of clear and cloudy trichs, not many ambers in site. The plants stigmas are receeding (which the diagram doesn't show and I think shows maturity in a plant) and the calyxes are swelling, yet not much amber. This plant could go further but may be ready at this point, and may never actually produce a large amount of amber trichomes.
It's sister, turns out to be an 8 week wonder, finished bang on with solid nugs and already 5% amber, same genetic background (selfed seeds).
This is an actual example of phenotypes that I grew.
You smoked number 1 and the sativa high is present yet when you relax the stone goes through your body and hey, this is an allrounder with a stoned yet heavy cerebral high effect. Awesome. Lets try the 8 weeker, by jolly, I'll be blown, it's almost bang on the same effect.
Okay, so different chromozones within the 20 present will deal with how the plant finishes and trichomes being there chiefly to protect the plant can change amber for all sorts of reasons, like us constantly touching the fukkers, movement damage, possible environmental, do the plants near your intakes look different in colour sometimes for example...and subsequently people basing their decisions on trichomes may lead to wrong decisions.
Different genetics produce different effects. Not all plants with equal trichomes will have equal amounts of strength, every plant and genetic line will have slight differences, which is why you base the plant on how you like to smoke them, but ultimately I say they are ripe when stigmas have receeded and calyxes have swollen and there is no further vegetative growth (i.e new stigmas being created) This to me is when a plant is finished. A sativa plant will give you a high mainly, an indica plant will give you chiefly a stoned body effect, hybrids will give mixes of these, and this is where the trick lies in finding your happy medium.
Sorry for banging on.
DST