How to specify cleanup commands for `systemctl disable --now`?

I just learned the (hard way) that in a systemd service file, the ExecStopPost commands are not executed on

systemctl disable --now myservice.service

They are only executed on

systemctl stop myservice.service

(which might then be followed by systemctl disable myservice.service). I have two questions on this: 1. What is the rationale behind that behaviour? 2. How can I specify cleanup commands that are also executed on systemctl disable --now?