Well, if you snip the trichomes off the top of the bud for the sample....If talking percentages, only percentages of active ingredients makes sense. The second someone says a percentage of plant weight is a particular active ingredient, they are bullshitting you. Lots of con artists operating in every walk of life, don't expect the weed scene to be any different
i've seen plants hit about 30%, once was watching someone operate the tests when it came back about 31%, i told them to go get another sample and test it again, the second and third tests came back about 29% so its legit on some of them, but the herb tasted like you where smoking hash, i think in a lot of other strains you may be getting similar total percentages but you have a larger chunk of it being terpenes then just thc