Ping - this is still present in 2021a-1+deb11u10 (bullseye).
Also, would it be possible for the "version 2021a" string in /usr/share/zoneinfo/tzdata.zi to be updated when you backport changes to that file? The 2021a-1+deb11u10 version of that file contains a number of backported changes from 2023c (such as Egypt DST changes) but an application that compares a tzdata.zi file with "version 2022a" to the 2021a-1+deb11u10 one with "version 2021a" will conclude that the latter is outdated and the former should be used. However, the 2022a file would not contain the Egypt DST changes, and the "2021a" from 2021a-1+deb11u10 actually does contain them. Could you add some kind of Debian-specific discriminator to the file? E.g. use "# version 2021a-1+deb11u10" ? That would still sort lexicographically before 2022a despite being newer, but it would at least allow an application to distinguish between 2021a-1+deb11u10 and 2021a-1+deb11u9. This is important for the GCC C++ standard library, which inspects that version line to determine if the file on disk has been updated and should be reparsed. A long-running application will not pick up the changes to your /usr/share/zoneinfo/tzdata.zi file if a sysadmin updates the tzdata package, because the version line doesn't change when you update it.