Thanks for the help guys. Sounds like maybe I'm being expecting a bit too much and a small amount of variance in the base is normal. My job requires inspecting things down to .0001"s of an inch, so I tend to be anal when it comes to consumer product defects lol.
For the record the board is flat enough where I can't see it by eye, and my nail doesn't catch in the transition between the ptex and the metal edge, so we're talking about a variation that is almost too small to measure. I just saw some very thin wax patches that didn't clean up as easily as the rest of the board and freaked out.