I have done full poweroff(8) before each DE test.

I did not configured them to start.

For some reason these DEs started them - do not ask me why - ask these DEs creators.

Packages on FreeBSD are rather 'vanilla' - only ported to work properly on FreeBSD - so its pointless to ask FreeBSD port maintainers here.

The only thing I configured to start were in FreeBSD main /etc/rc.conf config file:

    % cat /etc/rc.conf
    hostname="freebsd"
    ifconfig_em0="DHCP"
    sshd_enable="YES"
    moused_enable="YES"
    powerd_enable="YES"
    dumpdev="AUTO"
    zfs_enable="YES"
    dbus_enable="YES"

Regards.