Matt of course your correct. But I have not seen a smaller mfg have the chemists or equipment on staff to do the tests the big guys can. I was at Avonite's poly plant a few years ago for serveral days. I was impressed when they rejected several tankers of resin, and, in fact, shut the plant down the next day, while they waited for more tankers to arrive with resin. It did not meet their specs. They have 3o r 4 chemists that do nothing but quality control, plus spectomoters sp? etc. We have one of the larger small mfg here in Phoenix, I have been to their shop dozens of times. Trust me when I say they have nowhere near the checks that a company like Avonite does. With that said, does it mean all SS made regionally is bad ? Of course not, but, most of the cultuered marble guys that got into the business are no longer in it, there is a reason. Air curing makes it very easy to build in stress into the sheet, which may not show up for years.
It is much like material coming from Asia, some is great, some is marginal and some is horrible. When you can buy a white for $200 a sheet, why would you want to try to make it ?