Can't delete last rule in firewall ruleset 1.3.x

I think I may have stumbled on a bug, hoping for some clarity… I have a firewall ruleset called “ANY-ALLOW”:

vyos@vyos# show firewall name ANY-ALLOW
 default-action accept
 description "Allow all traffic"
 rule 5 {
     action drop
     state { invalid enable }

I decided to use global management to drop invalid traffic (set firewall state-policy invalid action drop) instead to clean up a lot of my firewall rulesets. When I go to remove this rule from my ruleset though, it fails:

vyos@vyos# delete firewall name ANY-ALLOW rule 5
vyos@vyos# commit
[ firewall name ANY-ALLOW ]
Firewall configuration error: Cannot delete rule set "ANY-ALLOW" (still in use)

[[firewall name ANY-ALLOW]] failed
Commit failed

I thought, OK, you can’t have a ruleset with no rules in it. However, that isn’t the case. I can create a ruleset with only a default action, and assign it in the ZBF while still not having any rules in it:

vyos@vyos# show firewall name LAN_MANAGE-to-LOCAL
 default-action drop
vyos@vyos# show zone-policy zone LAN_CAMS from LAN_THINGS
 firewall {
     name LAN_MANAGE-to-LOCAL
vyos@vyos# commit

It is important to be to be able to have rule sets with only default actions (another for “ANY-ESTABLISHED” with a default action of drop and no rules, to assign as my rule set for most outbound communication) for readability, rather than only default actions in the ZBF without description/explanation — by using the empty rule sets the intention is made more clear.

Moreso, at the very least there is a lack of consistency between my 2 examples that needs to be righted.