I can confirm this. Using different install options of Debian installer produce different sources.list. With default options selected of without internet connection user receives system that can't be updated and where many packages can't be installed without sources.list modifications
# STEPS TO REPRODUCE 1. Boot into official debian-12.0.0-amd64-DVD-1.iso 2. Select Graphical install 3. Proceed until step "Configure package manager" and question "Scan extra installation media?" 4. Leave default option ("No") 5. Finish installation, boot into system 6. check /etc/apt/sources.list # TEST RESULTS: 1. With "Scan extra installation media?" = "No" I've got sources.list with such content: ``` deb cdrom:[Debian GNU/Linux 12.0.0 _Bookworm_ - Official amd64 DVD Binary-1 with firmware 20230610-10:23]/ bookworm main non-free-firmware ``` 2. With "Scan extra installation media?" = "Yes" I've got sources.list with such content: ``` deb cdrom:[Debian GNU/Linux 12.0.0 _Bookworm_ - Official amd64 DVD Binary-1 with firmware 20230610-10:23]/ bookworm main non-free-firmware deb http://deb.debian.org/debian/ bookworm main non-free-firmware deb-src http://deb.debian.org/debian/ bookworm main non-free-firmware deb http://security.debian.org/debian-security bookworm-security main non-free-firmware deb-src http://security.debian.org/debian-security bookworm-security main non-free-firmware # bookworm-updates, to get updates before a point release is made; # see https://www.debian.org/doc/manuals/debian-reference/ch02.en.html#_updates_and_backports deb http://deb.debian.org/debian/ bookworm-updates main non-free- firmware deb-src http://deb.debian.org/debian/ bookworm-updates main non-free- firmware ``` 3. With Calamares installer from live media ("debian-live-12.0.0-amd64- gnome.iso") I've got sources.list with such content: ``` # See https://wiki.debian.org/SourcesList for more information. deb http://deb.debian.org/debian bookworm main non-free-firmware deb-src http://deb.debian.org/debian bookworm main non-free-firmware deb http://deb.debian.org/debian bookworm-updates main non-free- firmware deb-src http://deb.debian.org/debian bookworm-updates main non-free- firmware deb http://security.debian.org/debian-security/ bookworm-security main non-free-firmware deb-src http://security.debian.org/debian-security/ bookworm-security main non-free-firmware # Backports allow you to install newer versions of software made available for this release deb http://deb.debian.org/debian bookworm-backports main non-free- firmware deb-src http://deb.debian.org/debian bookworm-backports main non-free- firmware ```