How to list all units in systemd regardless of their state including parameterized / templated (@)?

OpenVPN unit file is parameterized (see @):

> ls /usr/lib/systemd/system/openvpn*
/usr/lib/systemd/system/[email protected]

The problem is that I cannot list the parameterized service names by systemctl command if they are disabled even with option --all:

> systemctl --full --all -t service | grep openvpn

However, I can still list names of non-parameterized disabled services (iptables in this example):

> systemctl --full --all -t service | grep iptables
iptables.service loaded inactive dead IPv4 firewall with iptables

How to get list of all units even if some of them are parameterized?

The question is actually more complicated (I could easily list available unit files to answer myself). However, the problem is in the inconsistency.

• When [email protected] service is enabled, it can be listed by the above command.
• When [email protected] service is disabled, it cannot.

It seems like an obvious bug (or limitation of the fact that systemd does not probably understand whether parameterized service is actually configured when we enable it). However, I rather ask the crowd than jump into this conclusion.