There are packages that need to add/remove inetd entries on install/uninstall. This is easy with xinetd, but AFAIK Red Hat itself recommends to develop on older systems to ensure maximal compatibility right now due to compiler/library mess^H^H^H^Hdecisions. Is there a recommended future-proof way to check, whether there is inetd or xinetd running on the target machine? I would say that a wrapper similar to chkfontpath, chkconfig etc. should be used - this does not solve anything for previous releases, but might help if there is similar change in the future.
There isn't a glibc/compilers mess, but binaries compiled on 7 aren't compatible with 6.2 due to use of new glibc (binary compatiblity is what we use to define a major series). 7 is a nice development platform, but if you need to deploy on multiple releases you need to compile with older libraries as the other ones aren't as uptodate yet. Anyway, inetd and xinetd are very different - the way to check for which one is present would be "rpm -q inetd" (or xinetd), and check if it is running with "service xinetd status" (or inetd)