Why Are My .json Filenames Cut Off?
Google truncates the name when it grows too long, so the .json no longer matches its photo exactly.
File systems limit how long a name can be. When a photo already has a long name, adding .supplemental-metadata.json pushes it over, so Google chops the middle out. The result no longer matches the photo character for character.
Simple scripts pair a photo with its .json by exact name. When the name is cut, they find nothing, skip the photo, and leave it undated with no warning.
Takeout JSON Metadata Fixer knows the truncation rules and pairs them correctly, which is why it finds dates on photos other tools quietly skip. It runs on your own computer and is free for your first 500 photos.