Same file exported to IOS Files and AirDrop differ. How to fix this?

Say I have a video or even a photo stored in my iPhones's camera roll(the Photos app). 1) I save it to Files(inside a folder) 2) Connect the phone to my Mac 3) Copy the enclosing folder using the Finder>iPhone>Files tab 4) Now I have the file on my computer Now... lets do the same, but with AirDrop 1) Select the file from the Photos app 2) Airdrop to my Mac. 3) Now I have a second copy of the file on my computer On first glance they look the same: same name and the byte count is(for the most part) the exact same. But, if I compare the two files with the command 'diff' it says they are different. Using an application to compare files byte-by-byte reveals that the top part, the header, is what differs. The files will be 99% the same. Does anyone know the specifics of how Airdrop and copying to Files causes the difference? There are also cases where the files differ in byte count. I would like to find a way to identify these duplicates and delete them. Ios version: 15.5 Iphone XS max thx