I probably bought the Guangxi of the auction Scipio is referring to because he posted the question with answer. It was advertised as a vintage stone which looked greenish in the pictures and had dark veins. As soon as I bought it he put up another one as BIN with the same pictures. I figured it was possible he cut a thick CF or worst case scenario another interesting vintage stone in half. So I bought that one as well.
As soon as opened the parcel they were obvious Guangxis. They also had circular saw marks no vintage stone has. So even if he didn't know they were Guangxis there was no chance someone with a little knowledge of hones could have mistaken these for vintage. He always takes pictures of the stones completely wet so you can't see the saw marks.
I returned them for a refund. I feel somewhat ashamed for falling for his scheme. This was just before people started posting pics of their veined Guangxis, bad timing. Anyway because I have dealt with him I can say that bacchus7-2007 is imho a total fraud, he can not be trusted. The fact he offers full refund if not happy is his failsafe for getting a bad rep. I explained to him these were Guangxis, however he continued to post them as unnamed ultrafine!!!!! hones for razors.
The two stones mentioned in the op are of a type often mistaken for CFs so it's possible bacchus7-2007 didn't know any better.
I am glad it sounds like you did get a CF, JeffE. I would like a closer look though :)