The goal is to harvest when thc content is maximized. Harvesting too early you might be robbing yourself of potency. If you wait too long, thc converts to cbn (or something like that) in which case you're also robbing yourself of potency. Basically the plant material is degrading at that point.
Trichs are just one aspect. Brown-receded pistils and swollen calyxes are other aspects. There's no "one size fits all" harvesting guide that applies to every plant.
Some plants will stay 100% cloudy for a month, or more, seemingly never going amber. Some go amber quickly, etc, etc.
If you;ve got all cloudy, and all the pistils have receded, and you don't see calyxes swelling anymore, you're most likely in the harvest window. And it is definitely a window. One day less, or one day more isn't going to make or break your harvest.
So true. It's a shame that bad advice has been so proliferated. Harvesting an indica early might give you a little raciness, but it ain't no 14+ week sativa high, not even close. I usually can't stand the high from any plant harvested too early, and I'm a sativa lover.