[semi-extrinsic]

From what I understand, the correct time stamps are maintained in the EXIF data when you export from Google Photos, and you can use tools like exiv2 on Linux to set the file modification timestamp to match the EXIF one:

  exiv2 -T rename image.jpg  

I don't think this is Google being actively malicious, but just file systems in general handling dates in a confusing way.

You can easily encounter exactly the same problem e.g. if you are copying images between systems with an external USB drive and you are not careful about how it's done. E.g. Windows Explorer will change the date to "now" if you do a simple copy, to avoid this you need to use "robocopy" or do a move instead of a copy.