Hi David,
Lightroom is using the XMP metadata section's photoshop:DateCreated for the Date and Time digitized. Photo Mechanic can adjust this date and time independently from the capture date and time. For your sample workflow, use Photo Mechanic's Adjust Capture Dates and Time from the Tools menu and set this to the date the film shot was taken ( June 25, 1993 ). Now to set the Date and Time digitized for Lightroom, open Photo Mechanic's Metadata (IPTC) Info dialog and set the Time and Date menu to the Date option. Now enter the Date and Time your digital camera took the shot ( April 29, 2020 ). If you have already imported this file into Lightroom, then select the file in LR and use the Read Metadata from File option in the Metadata menu. Now LR should show the correct dates for your workflow. I have attached a screen shot of Lightroom's Metadata panel set to the EXIF option for an image adjusted in Photo Mechanic 6. I hope this helps.
--Bob