Fedora is considered the "upstream" of RHEL... and so far as any "upstream" is a perpetual beta of a "downstream", ok... call it whatever you want. I guess that makes Ubuntu a perpetual beta of Debain? No? Why not?
In any event, there are a large number of differences between Fedora and RHEL. Take the biggest difference is the number of packages. If you want to call Fedora a beta for RHEL, call 1/10th of it a beta for RHEL because the other 9/10ths aren't even part of RHEL. I'm just guessing with those percentages... I haven't actually run the exact package numbers but you get the point.