From my experience and I have experimented a lot with this it's not a problem with Windows UAC nor with Poser external runtimes or such.

The simple truth is that it is a bug since Poser 4 there directories had been of low significance. Poser isn't using the path structure correctly. It's happening with obj-files absolutely every time and with image files used as material resource mostly every time. I never found out why it worked sometimes with images. For me from my programming experience it looks like Poser is not absolutely ignoring the path but by holding all entries in a internal list it looks like the search key in such lists is not set to the complete path AND filename structure than only to the filename. Therefor finding a file with identical name it looks to Poser like having this already without seeing that the path is different. So the deepth of search is not having impact. A deeper search will only last longer but gives no better result.

I have posted this problem while version 7 to the trouble desk and have had a longer mail discussion with the guys but we came to no satisfying solution. There was a bit trouble in discussion cause I used V4 (DAZ) for the examples and this is not a Poser original ... pou ... I was in hope that someone would find that bug while programming newer versions .... ok, hope is never dying ... :-))

The only workaround for this is indeed to rename such duplicate files and to edit the CR2/PP2/PZ2/MT5 etc. depending what is involved (obj or images).