This issue is still happening.
OPNsense 16.7.7-amd64
FreeBSD 10.3-RELEASE-p11
OpenSSL 1.0.2j 26 Sep 2016
root@vpn:/var/log # ps wwwaux | grep -i flow
root 73815 37.5 0.5 122160 32864 - Ds Mon05PM 1796:05.42 /usr/local/bin/python2.7 /usr/local/opnsense/scripts/netflow/flowd_aggregate.py
_flowd 85758 0.2 0.0 12360 2412 - Ds Mon05PM 13:34.98 flowd: net (flowd)
root 85525 0.0 0.0 12360 1560 - Is Mon05PM 0:00.00 flowd: monitor (flowd)
root 82449 0.0 0.0 18752 2196 0 S+ 5:06PM 0:00.00 grep -i flow
root@vpn:/var/log # ls -alh flow*
-rw------- 1 root wheel 33G Nov 3 17:06 flowd.log
root@vpn:/var/log #
OPNsense 16.7.7-amd64
FreeBSD 10.3-RELEASE-p11
OpenSSL 1.0.2j 26 Sep 2016
root@vpn:/var/log # ps wwwaux | grep -i flow
root 73815 37.5 0.5 122160 32864 - Ds Mon05PM 1796:05.42 /usr/local/bin/python2.7 /usr/local/opnsense/scripts/netflow/flowd_aggregate.py
_flowd 85758 0.2 0.0 12360 2412 - Ds Mon05PM 13:34.98 flowd: net (flowd)
root 85525 0.0 0.0 12360 1560 - Is Mon05PM 0:00.00 flowd: monitor (flowd)
root 82449 0.0 0.0 18752 2196 0 S+ 5:06PM 0:00.00 grep -i flow
root@vpn:/var/log # ls -alh flow*
-rw------- 1 root wheel 33G Nov 3 17:06 flowd.log
root@vpn:/var/log #