I forgot to mention that I was using sudo in each case.

Steps performed:
updated sources with
deb http://http.kali.org/kali kali-rolling main contrib non-free
deb-src http://http.kali.org/kali kali-rolling main contrib non-free

then
sudo apt update
sudo apt full-upgrade -y

Everything completed successfully with no errors. Logged off, rebooted, and signed back in.

Executed the commands in the description and no change.

Also ran the following for the new shell after:
kali@kali:~$ sudo apt update && sudo apt -y full-upgrade
kali@kali:~$
kali@kali:~$ cp -i /etc/skel/.bashrc ~/
kali@kali:~$
kali@kali:~$ cp -i /etc/skel/.zshrc ~/
kali@kali:~$
kali@kali:~$ chsh -s /bin/zsh
kali@kali:~$
kali@kali:~$ [ -f /var/run/reboot-required ] && sudo reboot -f

Rebooted still no change.

I know it's a bit late to answer, but VERSION="2021.1" was the latest released at the time of this bug report, in 2021-02-27. Seems like everything was fine, your system was up to date.