Do you reproduce with these files? there is no orientation field...
...I remember a long time ago in a galaxy far, far away that I've sent you some NEF files and you responded the same. In fact, the problem is more complicated because definitely
there IS another factor involved because if one will do a Rebuild Thumbnails on the very same set of files the new thumbs will have the correct orientation.
IIRC then you sent me a debugging version with log viewer enabled and we fixed the issue somehow. However now I don't remember what it was.
Besides that, it is very odd: How "is no orientation field" since the files are SOOC? Perhaps you're looking where it shouldn't? Perhaps the orientation bit is recorded somewhere else more reliably? ...or perhaps your the detection tool isn't written entirely correct?