Had a chance to do a bit of testing of Process Multiple Files
jpg with Quick Fix
I did one run on jpg files with no Quick Fix options checked and one run on jpg files with all Quick Fix options checked. The Quick Fix version produced images (modified jpgs in the destination folder) that were obviously corrected compared to the non Quick Fix run. No XML files were created, of course, and modified jpg files were output to a destination folder I specified.
raw with Quick Fix
I did one run on raw files with no Quick Fix options checked and one run on raw files with all Quick Fix options checked. The Quick Fix version produced images (modified jpgs in the destination folder) that were obviously corrected compare do the non Quick Fix run. No XML files were created, of course, and modified jpg files were output to a dfestination folder I specified.
Conclusion - contrary to statements by OP, Quick Fix options work exactly as expected in Process Multiple Files whether the input files are jpg or raw arw in this case. Michel, our assumption that Process Multiple Files will first apply ACR to the raw files using whatever the default ACR settings are, and THEN apply the PSE Editor's Quick Fix options is correcct.
The outputs from Process Multiple Files and Batch editing using ACR are different. PMF will only produce modified jpgs in the destination folder. Batch ACR will either open the file in the PSE editor for whatever further PSE actions the user wants to take or save an XMP file with ACR modifications to the original source file folder.