Confusing... about "This doesn't happen if source file is JPG". It really doesn't happen, if DateTimeOriginal is manually (using exiftool) added into JPG.
But, if xmp section is copied from DNG into JPG, then JPG behaves the same as DNG:
exiftool -tagsfromfile test.jpg -xmp:all result.mie
-copies complete XMP section into MIE, but using:
exiftool -tagsfromfile test.jpg -all:all result.mie
-now xmp:DateTimeOriginal and xmp:DateTimeDigitized are missing inside MIE.
Bogdan
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