A Tor qube gives stream isolation between qubes, as you would expect. It
also supports qubes firewall.
If I remember that thread, the questions was about use of the SocksPort.
I believe that Whonix ships with multiple traffic ports and configures
applications to automagically use ports. You would have to check the
source for confirmation.
Any one who wants to use the SocksPort can do so fairly readily from
downstream. Similarly more technical users can configure a Tor qube as
they will: it’s standard tor configuration. Some administrators do this
: most I know of leave it as a transparent proxy.
I never presume to speak for the Qubes team.
When I comment in the Forum I speak for myself.