You may have a sativa ish strain. Example I have one and fills a mason jar with 33g and then I have a indica that can put 70g of solid boulders in same size.
Also dsp's tight trim the sheet outta their buds.
Plus you ever read the label? They use a ton of boosters during the cycle.
even phenotype can cause this.. i grew out 15 clones from 5 different moms... all the same environment same soil light everything... some came out HUGE but fluffy and some were small but rock hard nugs... sadly my labeling was sub par... i still have some re cloned moms and some flowering now ... hoping some are the hard nug pheno lol and labeled much better this time!