Maybe it was started by dbus activation of the connman service.

In that case, the flag corresponding to disable-vpn? won't be passed since we
manually pass it to the shepherd service only.

It could be that then it tries to start up vpn but that dies because of the
unknown symbol and then the connmand also dies maybe?

When then started up by the shepherd service later (when you manually invoke
herd start networking) it will get the flag just fine and start up just fine
without vpn.

In short, it could be a timing issue.

If you invoke connmanctl without having connmand running already then dbus
activation would actually invoke it automatically (without flag), if there's
a service file for "net.connman".

But the error message from your other computer suggests that there is no such
service file, so it shouldn't have.