[SOLVED] Packages from buster backports in enterprise repository

The enterprise repository has (at least) 3 packages from Debian 11 (Buster) backports in them and they got installed onto our PBS:
Code:
# dkpg -l | grep bpo11

ii  kpartx                             0.9.4-5~bpo11+1                     amd64        create device mappings for partitions
ii  multipath-tools                    0.9.4-5~bpo11+1                     amd64        maintain multipath block device access
ii  multipath-tools-boot               0.9.4-5~bpo11+1                     all          Support booting from multipath devices

# apt-cache policy multipath-tools
multipath-tools:
  Installed: 0.9.4-5~bpo11+1
  Candidate: 0.9.4-5~bpo11+1
  Version table:
 *** 0.9.4-5~bpo11+1 500
        500 https://enterprise.proxmox.com/debian/pbs bookworm/pbs-enterprise amd64 Packages
        100 /var/lib/dpkg/status
     0.9.4-3+deb12u1 500
        500 https://debian.inf.tu-dresden.de/debian bookworm/main amd64 Packages

Is this intentional?
 
1. Debian 11 is bullseye, not buster (three b's in a row can be hard to keep track of ;))
2. the version number is wrong (it should have been ~bpo12+1), if you look at the changelog you can see it was a backport (done by us) of a newer package version needed for a bugfix at the time of the bookworm/PBS 3.0 release

thanks for reaching out! this does really look odd at first glance, so I can understand the confusion.