Loken's opinion that the battle host might deliberately expose him has two problems:
a) the GM could also do this, and aside from trusting in their integrity, there are simply no other options
b) an assassin does not create a zone of exclusion around itself that no NPC can enter. If there is additional reasoning for why the NPC moved there, then that's it, gg. Questions can only arise if the NPC made a completely pointless move straight to the assassin.