Digikam-Darktable timestamp mismatch

Recently, I modified the timestamps on some raw files I imported to Digikam. Digikam, doesn’t modify the metadata in the file directly, but instead creates a sidecar XMP file. However, I noticed that Darktable ignored the modified timestamps in the sidecar XMP.

Am I doing something wrong?

Is digikam producing sidecar files of the type filename.ext.xmp?

Yes, for example DSC03588.ARW.xmp. Captions set in Digikam do propagate through the XMP file to Darktable, so I know it does load the XMP file.

What tag and what group?