I received a reply from PNW several days ago. Their suggestion was to avoid carbon paste since it can sand through anodized surface and lead to corrosion causing a stuck seatpost. This is contrary to the advice in the FAQ of their own website. Their suggestion was that if the new weird seatpost clamp doesn't work out then I can contact them for an exchange. The idea being that standard black might be a teeny bit grippier than the silver I have.

I took out the post again and replaced the clamp with the weird red one pictured earlier in this thread. It fits perfectly and essentially doubles or more than doubles the clamping surface area. That is extremely encouraging but it doesn't seem as heavy duty as the OEM Canfield clamp I had. I don't take drops with my seat up, it hopefully won't matter. Despite manufacturers advice, I did reinstall it with a small bit of carbon paste.

I truly hope that's the end of it. I hope it'll be a year or two before I have the post off again.