You are mistaken. You might have been expecting that NPTL would be
installed in /lib/tls and that libraries not in /lib/tls are not
TLS-supporting, NPTL-using libraries. That is not the case. In FC4, the
TLS-using libc and the NPTL libpthread are the only ones really supported,
and those are what you see in /lib. /lib/obsolete/linuxthreads has what it
sounds like, and you have to try hard to get it if you really want it.