Here's something I find baffling.
The differences between 1.jpg and 2.jpg is that the latter is stripped of EXIF data and the file size is obviously smaller.
Useful to know if you want to keep the EXIF data with the .jpg (or not). Is there a simple explanation for this?
As I read your bullet list, 1.jpg is effectively created from the original jpg (using its EXIF data) despite the fact that you have saved it as a cpt whereas 2.jpg is created from the cpt (which, of course, has no EXIF data).