Prior to this patch, events on interfaces that couldn't possibly be part of a PF ALTQ configuration, such as vlan(4), would trigger a copy-existing / install-new / teardown-old PF ALTQ configuration cycle. This would result in needlessly lengthy vlan(4) creation times on systems with active PF configurations that had a large number (hundreds or thousands) of queues. On such systems that also employ hundreds or thousands of vlan(4) interfaces, the time required to create those interfaces became untenable.
Tested with a pf.conf containing ~4k queues. vlan(4) creation times are reduced from ~200ms each to < 10ms each.