Why is it that when a hash company puts out several batches from different plants...

...for sale, the test results are almost always within a very narrow range? I've been noticing this more and more on recreational websites' menus. It bugs me. I'm looking at a page right now with 14 different kinds of rosin from one manufacturer and most all the tests are within 1% of each other. One tests out at 76.7% THC and a completely different strain from the same company tests out at 76.5%! How is that even possible? Has hybridization made everything that closely related when grown under specific conditions? Or...is there something funny going on with the testing? Because when another brand shows up for sale, their strains also vary widely, but test results are always very close. It's like each company must pay the testing company to provide them with a set of test results within a certain range....Or, maybe they don't even really test the stuff at all anymore and the company just makes up their own results?

There is said to be a lot of pressure and buy outs, of dispensary to the test center's.
Everyone loves to buy a high thc strain, if you make them all high thc, everyone buys!
But yeah some test centers get pressured into fudging the numbers.

The majority of modern recreational strains are high in thc, and low in other cannabinoids. So, by definition, concentrates made to a similar quality from those strains should have a closer range of thc numbers than the flowers they come from.
1g of rosin from a 13% flower could be 75% thc and so could 1g of rosin from a 26% flower. But you'd get twice as much of it from the 26% flower.