For me, judging harvest timing based only on what the trichomes appear to be is not 100% foolproof.
I have had plants that have 70%+ amber trichomes after only 4 weeks of flowering which then needed another 6 weeks or so to fully develop and I have had other plants that never had any amber trichomes at all.
My most reliable signpost for overall plant maturity is pistil condition.
Once there are 98-99% brown pistils is when I harvest and this will usually coincide with 10-30% amber, 60-70% cloudy and 10-20% clear pretty reliably across "normally" maturing plants.
Once there are 100% brown pistils, the plant is on the cusp of death and a near dead plant can not maintain peak trichome quality, this is why I aim for 98-99% brown pistils..........the plant is fully mature, but not quite in the downward decline into being over ripe and with death approaching.
I have been doing this for 35+ years now, it works for me and is far easier than trying to judge trichome colour percentages.
Waiting for trichomes to hit a magical percentage of amber has many variables and in my experience, can not be relied upon across all plants in all situations.