Just ran “cat /etc/os-release’ on my two Pi 4Bs and noticed one uses Raspbian Bullseye and the other says Debian Bullseye. I used the same official Raspberry Pi imager but likely updated the imager in between. Just curious if there are any differences besides the names in os-release. 
Raspberry Pi OS was originally based on the armhf implementation of Raspbian which is a 32bit ARM6 OS which will run on all Pi up to but excluding Pi5.
The 64bit OS (which was introduced in Feb 2022) is based on the normal Debian upstream (although with a few Raspberry Pi Ltd. modifications) which will only run on the later model Pi. Except for these it uses normal Debian binaries for most of its code.
