PF binat rule issue - feature or bug?

[Greg Barniskis]

Using 7.2-RELEASE-p4 i386 with GENERIC kernel, I've found (the hard way) 
that if I have a pf.conf rule like

nat on $ext_if proto { tcp udp icmp } from $my_subnet \
   to any -> some.public.ip.num

then pfctl will perform the expected expansion of the listed protocols 
into three separate NAT rules.

However, if I have a rule like

binat on $ext_if proto { tcp udp icmp } from $server_dmz_ip \
   to any -> $server_public_ip

then I will /only/ get one NAT rule, for TCP.

Then things like NTP, DNS and ping will fail, but the filtering rules 
that permit such traffic will increment their byte, packet and state 
counters like PF is working just fine (and I suppose in some sense that 
the filtering part is). But only if I explicitly declare in pf.conf a 
separate binat rule for each desired protocol, instead of listing them, 
will things work as needed.

Feature or bug? If the former, it is not well documented that I could 
see. I expected that a list of protocols for a binat rule would just 
work, and pfctl certainly didn't mark it as bad syntax. If a bug, is 
this a FreeBSD bug or OpenBSD?