Yes, because it in itself the xpgt is a valid file. The mediatype that is assigned to it "application/vnd.adobe-page-map+xml" is actually a semi-vaild (debatedly) mediatype. The problem is it is a mediatype for a different kind of file!
The way to correct this is to replace the wrong mediatype for the .xpgt file with the correct one for this file type. According to the mobileread wiki,
https://wiki.mobileread.com/wiki/Ado...ayout_Template
It should be "adobe-page-template+xml" or under the new iana.org try a "vnd.adobe-page-template+xml".
This is why this is so troublesome. The assigned mediatype did not match the file extension but does actually exists at least according to some people.