Seed banks and breeders exaggerate flowering times to appeal to cash croppers for the most part. People who make a living growing are typically trying to turn runs over as fast as possible and don't always care if the plants are 100% ready. It doesn't help that a lot of new growers starting out have grown up in this internet feuled age of instant gratification where there is a wiki for every subject, a YouTube tutorial for every occasion, and anything you want is 2 days away with an Amazon prime membership. Doesn't tend to make for patient, meticulous growers. Everything has to be huge and it has to be right now!