Hold Steady/Act under Fire is also the move that's closest to being imposed on a PC from outside. When there's "fire", or "pain, danger, urgency, impatience, or emotion", and you do anything in spite of that "fire", you've got to roll it. If you're doing also Claiming your Right, or Going into Battle, or making any other move, you've got to roll Hold Steady first. Hold Steady/Act under Fire is basically an extra chance to roll a miss, because conditions are worse. It actually seems fairer to me that the 7-9 outcome is "carry on", rather than "carry on, but...". That's my take on it anyway.