initrc_t is also impacted: it can send query but not receive result:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
# sesearch -A -s initrc_t -c dbus -t systemd_hostnamed_t
allow dbusd_unconfined nsswitch_domain:dbus send_msg;
allow dbusd_unconfined systemd_hostnamed_t:dbus send_msg;

# sesearch -A -t initrc_t -c dbus -s systemd_hostnamed_t
--> nothing
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Thank you for reporting this issue, I've cloned it for further checking and resolving in Fedora.

Can you explain what is the severity of this bug and what is the use case for running commands like hostnamectl from a rpm scriptlet?

We do not control which program is executed from rpm scriptlets, especially for 3rd party packages.
For now there is no use case, but it would be good to browse the policy once to detect all search missing rules, i.e. where a source domain can send the message to a target domain but not get the response because the target domain cannot send back messages to source domain itself.

Ideally an automated script should check for such rules, e.g.:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
# Get all rules
sesearch -A -c dbus -p send_msg > /tmp/dbus_send_msg.rules

# Print rules that don't have "reply rules"
while read _ src tgt _; do tgt=$(echo $tgt | cut -f1 -d':'); grep -q "^allow $tgt $src:dbus" /tmp/dbus_send_msg.rules || echo "$src -> $tgt OK but no $tgt -> $src"; done < /tmp/dbus_send_msg.rules
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

The script doesn't handle attributes, but the idea is here.

As no new information appeared during the past weeks, we are going to close this bug. If you need to pursue this matter further, feel free to reopen this bug and add justification.

Progress can be tracked in the following Fedora bz:
https://bugzilla.redhat.com/show_bug.cgi?id=2170059