I just looked at Date and it is the 12/7/25. I've never understood where the Date comes from.
In the Metadata Template, the date defaults to whatever the date is when Photo Mechanic's Preferences were created. If the date is different than that, it is due to some action by the user. This could either be changing it by hand, or if you have the dropdown set to 'Date' on the Metadata Info window and hold the option/alt key to and use the "Copy to Template" button in the Info window by holding the option/alt key with the window open. The metadata Template will switch to the "Date" option and enable it if you load an XMP file that has an "xmp:CreateDate". So perhaps you did this at some point.
Why would the .xmp file that Photo Mechanic writes use this hidden date and not the Capture Time?
I can't reproduce any situation where it write the date when it's "hidden". When my Metadata Template is set to Capture Time and the Apply box is checked, "photoshop:DateCreated" and "xmp:CreateDate" get set to my images' capture time, which is sourced from the Exif data written by the camera.
When you say "date box checked" what happens if it is not checked? I always assumed checking the Date box and setting it to Capture Time is the correct workflow.
If an XMP file doesn't yet exist, or it exists and "photoshop:DateCreated" and "xmp:CreateDate" don't exist in the the XMP, then it it updates them with the capture time. If they do exist, then it simply won't update them.
The best practice is to leave the checkbox for the date line unchecked in the Metadata Template unless you have a specific reason for the IPTC date to be different than the capture time.
Photo Mechanic sets the correct time that is in the camera metadata that it and the Finder reads.
Finder is showing the File System's creation date value, not the Capture Time. Typically these will be the same (especially when a digital camera created the file), but its possible for them to differ (an image may have been capture 50 years ago but the file may have been created today) . Via the "Adjust Capture Dates and Times" option in the Tools menu, you can update the Capture Time independently of the file system's creation date by unchecking "Also update file creation date/time".