I mean, where in the hell would an entire army fire at a single noble's unit and ignore a battlefield full of warriors? It just doesn't make the slightest sense.
This tactic has done a great job revealing a tactical/technical fallacy in the combat code that must be rectified as soon as possible.
Just hate it... pure nonsense and people are exploiting it all the time in every continent. Bug or not, code error or not... it's revolting.