I think that this fits nicely with everything that we have seen thus far. His freezing up and being able to swear the oath in Shadesmar and nearly giving in to Moash in Hearthstone does seem to follow this dynamic. In Shadesmar they were outnumbered and Dalinar chose to confront Odium. There was nothing that he could do to stop what was going on here. Shallan and Adolin were fighting back against a superior force with little chance of survival. Odium a Shard could flatten Dalinar and Kaladin could only watch. Moash hits him that eventually everyone that he cares about will die. Kal cannot really deal with this. He is consumed by this inability of others to make their own choices and live with the consequences. In a way it is poetic for Shardplate to come with this oath. It is a form of protection and strength to help one overcome some decisions that a person might make on the battlefield. It may not always succeed, but it adds agency to people to make dangerous choices which may yet still be the right ones.