The dupe detector isn't working properly on these ones.

Try downloading it and then run it through http://moe.imouto.org/post/similar It doesn't get flagged. I has the same issue with the version from the AP torrent. Some of Midzki scans have this same problem.

I'll see if I can through to piespy on IRC

Hmm, do you know how the tool gets the posts it searches? If you search the sample at http://iqdb.hanyuu.net/ nothing comes up either.
I know it doesn't search held posts until they are released, and I suspect it has problems with posts that are held for a long time (if I remember correctly, a couple weeks for this image).

Very good point.

I just tested a short-term held image and it has the same behaviour. Must be some flag on held images not being removed when activated.

This will have to go on petopetos bug list.