Re-importing iPhone ProRaw DNG files back into iPhone Photos to batch convert using RAW>HEIC shortcut.

We have about a thousand DNG files that were downloaded from an iPhone 14PM to a Windows-based drive in DNG & JPG formats. I want to batch convert these to HEIC and would prefer to use the Raw > HEIC iPhone shortcut that I am now using on current pictures as part of my download process.

I have scoured the web and tried several approaches (incl. iMazing, Google Photos). iMazing (like iCloud) will not upload a useable DNG back to the phone it was shot on. Google Photos uploaded DNGs the first time such that I could see the original IMG_XXX file name (likely from the EXIF data) & files sizes in both Photos and the DCIM folder; however, the images were non-functional in both Photos and DCIM. Next, I renamed the DNG files back to their original IMG_XXXX number and tried again and subsequently the images were showing in Photos and DCIM as TIF files but any processing I tried to do said they were actually JPG files.

Am I missing something on how to do this or is reloading an iPhone DNG image back to the iPhone just not possible and I'm wasting my time trying.

If this is just not possible, I'm starting to look for DNG>HEIC converter programs to see how their quality compares to the iPhone shortcut output but thus far am only finding online programs (not comfortable doing this for the moment but may reconsider) or something very expensive. For a PC based program the best I am finding is to maybe convert DNG to TIF then TIF to HEIC but before I start testing this I thought I would ask for some help ......

Thank you for any guidance