GIMP file association is not up to date on OSX (plist related)
In the GIMP 2.10.4 build for macOS, XCF files are no longer properly associated to open with GIMP, nor will files load via spring loading (dragging a file to the GIMP icon on the dock) or through the Finder.
This behavior is caused by the removal of exported UTIs in the Info.plist bundled with GIMP (XCF is not a native file format to macOS, and setting up Document Types to an undeclared format is not recognized). GIMP 2.8.22 and earlier still contained the proper table and behaved normally in that aspect.
Edited by Alex Samorukov