Rule ordering changes

I've been scratching my head over this one.  Here is my pf.conf:

int_if = "em0"
dmz_if = "em1"
block log all
set skip on lo0
block log quick inet6
block in  log quick on $int_if from ! <rfc1918> to any
block out log quick on $int_if from any to ! <rfc1918>
pass  out log on $int_if inet proto tcp from $int_if:0 to 10.1.1.1 port ldap
pass  in  log on $dmz_if inet proto tcp from $dmz_if:network to $dmz_if:0 port ldap
pass  in  log on $dmz_if inet proto icmp from $dmz_if:network  to $dmz_if:0
pass  out log on $dmz_if inet proto icmp from $dmz_if:0 to $dmz_if:network
pass  in  log on $int_if inet proto icmp from <rfc1918> to $int_if:0
pass  out log on $int_if inet proto icmp from $int_if:0 to <rfc1918>
pass  in  log on $int_if inet proto icmp from <rfc1918> to $dmz_if:network
pass  out log on $dmz_if inet proto icmp from <rfc1918> to $dmz_if:network
pass  in  log on $dmz_if inet proto udp from $dmz_if:network to $dmz_if:0 port ntp
pass  in  log on $int_if inet proto tcp from <rfc1918> to { $int_if:0 $dmz_if:network } port ssh
pass  out log on $dmz_if inet proto tcp from <rfc1918> to $dmz_if:network port ssh
pass  out log on $dmz_if inet proto tcp from $int_if:0 to $dmz_if:network port ssh
pass  out log on $int_if inet proto udp from $int_if:0 to <dns> port domain
pass  out log on $int_if inet proto udp from $int_if:0 to <ntp> port ntp


The problem is that some rules end up out of order in the "pfctl -s rules" output (note the icmp rules in particular):

     0   block drop log all
     1   block drop in log quick on em0 from ! <rfc1918> to any
     2   block drop out log quick on em0 from any to ! <rfc1918>
     3   block drop log quick inet6 all
     4   pass in log on em0 inet proto icmp from <rfc1918> to 192.168.7.2
     5   pass in log on em0 inet proto icmp from <rfc1918> to 192.168.8.0/24
     6   pass in log on em0 inet proto tcp from <rfc1918> to 192.168.7.2 port = 22 flags S/SA
     7   pass in log on em0 inet proto tcp from <rfc1918> to 192.168.8.0/24 port = 22 flags S/SA
     8   pass out log on em0 inet proto udp from 192.168.7.2 to <dns> port = 53
     9   pass out log on em0 inet proto udp from 192.168.7.2 to <ntp> port = 123
    10   pass out log on em0 inet proto tcp from 192.168.7.2 to 10.1.1.1 port = 389 flags S/SA
    11   pass out log on em0 inet proto icmp from 192.168.7.2 to <rfc1918>
    12   pass out log on em1 inet proto icmp from 192.168.8.1 to 192.168.8.0/24
    13   pass out log on em1 inet proto icmp from <rfc1918> to 192.168.8.0/24
    14   pass out log on em1 inet proto tcp from <rfc1918> to 192.168.8.0/24 port = 22 flags S/SA
    15   pass out log on em1 inet proto tcp from 192.168.7.2 to 192.168.8.0/24 port = 22 flags S/SA
    16   pass in log on em1 inet proto tcp from 192.168.8.0/24 to 192.168.8.1 port = 389 flags S/SA
    17   pass in log on em1 inet proto icmp from 192.168.8.0/24 to 192.168.8.1
    18   pass in log on em1 inet proto udp from 192.168.8.0/24 to 192.168.8.1 port = 123

This is under OpenBSD 5.1.  Am I misunderstanding something?  Is some kind of optimization taking place behind the scenes?

Andy