The sample caps just arrived, thank you very much, infiniti!
At first glance these have a significantly rougher texture than Cherry PBT, it's maybe a little rougher than Imsto PBT, the color of the milky white one is a tad more yellow than Cherry PBT, which is in turn warmer than the white Imsto PBT . The grey one seems to match grey Cherry PBTs quite well, it is a tiny bit colder, though. Compared to slighty yellowed Cherry ABS keycaps, the milky white seems to be spot on to mine, but that depends on the yellowing grade. The thickness seems to be the same, accurate measurements will follow.
I'll post a more thorough comparison soon!