Do you know the source of yours? I believe the porcelain form originates from Longwood Gardens of Pennsylvania and it should maintain a flat peristome. The body should also be unmistakably leathery, similar to lowii. There are some plants in the states labeled "porcelain" but they look nothing like this, so I'm not sure how that happened.
Mine came from EP, it's their (c) clone. So if it's placed in a sunny position, the interior darkens up quite a bit and the exterior becomes a creamy colour. There is also the (d) clone, which unlike (c) remains quite pale as it ages. These as far as I understand were sourced a long time ago 20 years + from wild cuttings. I've read that other "porcelain" forms or "alba" forms as they have come to be known, also came from Kew & Malestiana Tropicals.
Also both (c) and (d) are females and I can't speak for (d) as I don't own the clone, but like you say (c) is as woody as lowii pitchers, especially as they age.