The two times I've gotten grassy flavors from dry-hopping, the hops were in the keg for over 8 weeks. In one case, the hops were right off the vine; a proceedure I do not recommend. I left the hops in hoping it would get better. The flavor went from odd to grassy.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk