is fedora really bleeding edge?

[Stuart McGraw]

One of the reason for using Fedora is quick access
to the latest software -- sometimes even too quick
(hence the "bleeding edge" moniker.)

But I have noticed this is not true for some things.
For example, in Fedora 15 python seems frozen at 
python-2.7.1 even though -2.7.2 was released a long 
time ago and fixes a number of bugs.

Another example is postgresql which remains in the 
9.0.x release although 9.1.x contains a number of
significant new features.

Why do many packages follow the upstream faithfully
yet others seem to use a boat-anchor update policy?  
Is there an official policy about this or is it a 
matter of individual packagers' choice?