Why do I run Linux version 5.10 after upgrading to Debian 12 instead of version 6?

I upgraded from Debian11 to D12 and cat /etc/debian_version, KDE Info Center, lsb_release -a and all other ways to show the current Debian version show and showed Debian 12. The upgrade seems to have worked just fine and I have used the system for several months (including several reboots) and over that time upgraded to Debian 12.7. There was never any error / message about the kernel and nothing is asked to be installed when running sudo apt-get dist-upgrade or sudo apt-get upgrade (except sysv-rc-conf). Despite of all this, I'm apparently running a Linux kernel of version 5 - when running cat /proc/version it returns: > Linux version 5.10.0-17-amd64 (debian-kernel@lists.debian.org) (gcc-10 > (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) > 2.35.2) #1 SMP Debian 5.10.136-1 (2022-08-13) **Why did this happen?** Aren't all methods to see the current Debian version broken if they all show version 12 if I still have a kernel of version 5 and isn't the distro-upgrade process broken as well? I only found out when my mousewheel broke but should have broken earlier right after upgrading to Debian 12 with Wayland since xbindkeys should not work with Wayland since I then noticed gcc-10 was used here . apt policy linux-image-amd64 shows:

linux-image-amd64:
  Installed: (none)
  Candidate: 6.1.112-1
  Version table:
     6.10.11-1~bpo12+1 100
        100 http://ftp.XY.debian.org/debian  bookworm-backports/main amd64 Packages
     6.1.112-1 500
        500 http://security.debian.org/debian-security  bookworm-security/main amd64 Packages
     6.1.106-3 500
        500 http://ftp.XY.debian.org/debian  bookworm/main amd64 Packages