There is nothing anecdotal about learning how a plant grows and knowing when to harvest based on experience. I've literally grown well over 1k plants in the last 10 years dude.
Harvesting early reduces weight, flavor, smell, density, and quality of the high. It does this by not allowing the plant to finish the maturation process which includes the buds swelling internally increasing the weight and density. Throughout the maturation process the plants also increase terpene production and resin production which if you chop early you miss out on.