You cannot go on leaf yellowing to judge harvest time!
The hell you can't! I've done it many times. Nutrient lockout? Sure, if you create problems like that for yourself, then I agree, don't go by the leaf color.
More sunlight is better? Well no shit. But once that plant has effectively finished its reproductive cycle, it doesn't matter how much sunlight you give it. It's done growing, period.
EDIT: Nutrient lockout is a hydro problem. If you get nutrient lockout growing in soil, then it is time to find another profession.
Leaf yellowing is the best determinant of when an outdoor plant is "done" because all strains yellow out the same way regardless of whether they finish early or late. First the lower leaves go yellow, then the middle, and lastly the top. You can wait until the thing looks like a banana but then you are going to have narco weed due to the increased CBD content. When the top fan leaves start to yellow, that plant is DONE.