darktable can't reload *.xmp file modified by digikam on startup.

Hi All, As title. I use win10 and dt 2.7.0+1945version.
For example:
I tagged 4 starts on some photos in darktable, then I startup digikam, I can see the changed.
But when I tagged photos in digikam, startup darktable. I can’t see the changed.
I need to reimport the folder, then the changes would be shown.

I have checked the item “look for updated xmp files on startup” in darktable.