Section 3 is rather general, and doesn't directly address this issue. The statement in section 4, because it only "encourages", clearly shows this is not a requirement.
It can also be taken like how the FSF encourages Debian to "rm -Rf non-free" on its mirror servers: We can't require you to, but if you don't, we won't approve of it.
I take it to mean that people are urged not to use licenses like TeX's license.
Yep. We urge people not to use that exception