The Match and Limited are more top-end guns than the one the original poster was asking about.
When I first replied I was thinking about the less expensive models -- like the one he was asking about. I doubt you'll find polygonal rifling in those guns. When he talked with EAA, he may have asked about the specific gun he owned (I would have done that) and not a more general question, so the answer he got could've been absolutely correct (and not someone speaking out of ignorance.)
I've owned a number of Witness handguns, including their older Long Slides (one in .40 with a small frame, and one in .45 with the larger frame); the Long Slides were the predecessors of the newer, higher-end guns. I've also had several .45 larger framed plain-jane models, one 10mm and a bunch of 9mm and .40s models with the smaller frames. They all had the conventionally rifled barrels. The polygonal barrels must be a newer enhancement (maybe the last 10-years or so?)