[brazen1]

Is this as DV is not playable on Windows?

Dolby Vision is playable on Windows using the Movies & TV app plus a couple components from the Windows Store.  It isn't true Dolby Vision for me because I don't prefer a Dolby Vision capable display but playback does look very, very good imo

Or do I have to manually rename my files to recognise dv tag?

I always include tags in my file names.  Why don't you add DV to one of your file names, rescrape, play the main title for a couple seconds, and see if the DV icon shows up with the rest of the metadata icons?  If it does, then you've answered your own question.  You can even have HDR10+ and DV in the file name if your title includes HDR and DV video.  (some.movie.year.2160p.x265.uhd.atmos.hdr10+.dv)  DV will override the HDR10+ tag and display the DV icon only.  If there is no DV in the file name, then the HDR10 icon will display.