Cav or phalanx armies are not affected (well, this limits the benefits of this tweak to barbs only..), as they have their own formations, with 2.0 priority.
/EDIT Or what Kraxis said..
I guess the formation selection system first tests if the army can fill the requirements for highest-priority formation, if not it checks the next one etc.
We could also write some better formations for AI to use.
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