When creating a firewall alias and then deleting it later the alias still lives on in the drop down menu of the firewall diagnostics until a reboot. This is on 25.10.2
What you see in the firewall diagnostics is the pf table.
Check "pfctl -t my_alias_name -T show" from the shell
It should show the table with its contents, after a reboot PF can remove it so it will be gone.