It’s actually a really good question. What you’re explaining is called a collision, by creating the same hash with different numbers you can succesfully login.
This why some standard hashing function become deprecated and are replaced when someone finds a collision. MD5, which was used a lot to hash passwords or files, is considered insecure because of all the collisions people could find.
You can also configure vim to use the first clipboard (works with nvim but never tested on vim).