That is, there is the odd jpg where the lens name is in the XMP although not in EXIF. Mostly not, but occasionally it has, in PL 4.1, 4.2 or 5. So I have looked over other jpgs exported from PL to see whether this has happened. Looking at the details of the jpg in EXIFTool Gui, I notice that the lens name is not in the EXIF but has been written to XMP-aux - I can only surmise that Flickr read it from there. To my surprise the lens name showed in Flickr. I tried your test - processed a RAW file in which the lens name was only in Maker Notes (usually I copy it to EXIF using EXIFTool Gui, before processing, but not for this one), exported to jpg and uploaded to Flickr. I couldn't see any instances of this before PL4. My guess is that these are images in which, for some reason, I neglected to copy the lens name from Maker Notes to EXIF and somehow the software has put it in XMP. Perhaps it's not saved to EXIF, but in a format that is readable by Flickr, while it was not done so before.I tried your test - processed a RAW file in which the lens name was only in Maker Notes (usually I copy it to EXIF using EXIFTool Gui, before processing, but not for this one), exported to jpg and uploaded to Flickr. Lens name shows up only in the second picture. See those two pictures, one the OOC jpg, the other the file as converted by DxO PL5. I don't think it's a feature of the K-3 III.

Dxo filmpack 5 kodachrome