Hay flavor is also from harvesting too early. The plant doesn't start really pumping out essential oils and terps until later in flower. Buds harvested at 6 weeks will not be anywhere near as smelly or flavorful as those harvested round weeks 8-9 when they're ripe. Obviously talking indica or shorter flowering strains as a basis for this conversation. As an example, I had to chop an entire crop at week 5/6 due to hermies. I dried and cured that crop just the same as any previous harvest but the smell and flavor never came out in the cure. I can assure you they weren't dried too quickly. That entire harvest is reserved for cooking because smoking it tastes like I'm smoking lawn clippings. To top it off, the stone is mild, short lasting, and very racy, not really enjoyable unless mixed with other weed. I would personally rather just smoke the other weed because it tastes better!
I completely agree with the 10-20% amber. I find that to be my sweet spot for harvest. I feel like most people harvest too early. It's the excitement or the impatience that gets 'em. Breeders listed flowering times are nonsense. Most everything I've grown went 1-2 weeks longer than suggested by the breeder. I'm cutting them based on what i see in my loupe, not what i see on the breeder pack.