git filter article

After implementing the [git filter suggested here](https://seankhliao.com/blog/12020-09-24-gitattributes-age-encrypt/) I noticed that after cloning the project in another location I have a staged change in an encrypted file. `cat`ing the file shows the expected unencrypted content, but `git diff`ing the file shows differences in the encrypted amored text.

I wonder why this happens, any idea?