You mentioned the game config, but I assume you are talking about the control key function -
<keymapdata>
<name>Set Stance Passive</name>
<displayname>$$22332$$Set Stance Passive</displayname>
<event>alt-s</event>
<context>game</context>
<command>unitSetStancePassive()</command>
</keymapdata>I am pretty sure this this works as it should, but some of the Norse units act a bit strange because they are both builders and soldiers and my guess from trying to get the standard AI to run some of my own units is that the attacking takes precedence over the building.
What I think happens is that the unit may initially continue to build/gather/whatever, but once the AI requires more attack units it will be allocated to that AIPlan in precedence over the BuildPlan.
Unless the buildplan has a higher priority (and from memory by default they don't) a combined economic/military unit will always be grabbed for military stuff first.