preupgrade: can it upgrade system to latest set of updates?

After using preupgrade to upgrade a number of machines, we notice that 
the whole process of upgrading involves running preupgrade and then 
after it finishes running 'yum update' which again updates about 3/4 of 
the packages already updated by preupgrade.  Isn't there some way that 
preupgrade could just load the very latest updates while it's doing the 
upgrade instead of requiring the user to update each package multiple 
times?  This sure would cut down on the total time necessary to upgrade 
these machines.

Regards,
Gerry