In North American, Sichuan peppercorn can have a vast amount of seeds and stems. It really can vary. I've seen packages where 50% of the peppercorns still had their pits. Other times I've seen packages with less than 25%. Either way, it's clear. North America has bad Sichuan peppercorns.
If less than, let's say... 25 percent? of your peppercorns, have their seeds - there's no problem grinding them. It's hard to tell the difference in quality from 5% pits and 10% pits. It's when theirs an exorbitant amount of pits that the "gritty" texture comes about.
But if peppercorn producers aren't drying the peppercorns right, then there's probably a lot of other corners they're cutting. Often people attribute Sichuan peppercorns atrocious quality in the US to a ban on Sichuan peppercorns in America by the USDA. This is false.
The ban was lifted in 2005 with the caveat that they must be pasteurized at "140 degrees Fahrenheit or above for 10 minutes or longer" to kill off any citrus canker bacteria that may be present. So it goes, this "pasteurization" is what's causing the low-quality peppercorns in the US. But how does that explain the massive amount of stems? All of the seeds in the bag? And can heating peppercorns to 140f really cause the peppercorns to lose so much flavor? I don't think so personally. This is substantiated by Taylor Holiday, an exporter of high-quality Chinese ingredients.
"There is little discernible difference between those Sichuan peppercorns that had been heat-treated for export and those that hadn't... There's no excuse for the inferior, lowest-priced product, packaged years ago, sitting on US shelves besmirching Sichuan pepper's good name."
I think it's fair to say that the US is getting the worst of the worst exported to us. There must not be enough demand for quality Sichuan peppercorn. Most of the time, the quality doesn't matter. As long as your bag doesn't have massive amounts of seeds and stems, you'll be okay. You may need to add more peppercorn to get the same numbing hit. Though, If you genuinely care about good Sichuan peppercorns, I'd recommend picking them up from Épices de Cru or perhaps The Mala Market. The downside is they are pricey. Save the good quality ones on a dish where the mala flavor profile is being fully utilized. For example, if you're making kou shui ji, you should definitely use the good stuff. If you're just adding some Sichuan peppercorns to a red oil or to cut the gamey-ness of meat in a quick marinade, use the cheap ones.
