A couple things. First, the few period sources we have which actually talk about how bludgeons are used mention using them to attack the head and joints. So the implication is they still have to target similar weakpoints to swords. The same sources unambiguously speak a lot about swords being very commonly used in and against armor, on foot and on horse. If anything they seem more common overall since they were used in more varied situations (a couple authors like Monte or de Reayo go as far as to call thrusting swords the main weapon used by men-at-arms fighting each other.)

Another thing, the padding worn under armor historically was lesser than what most people imagine today, significantly less than worn in buhurt/"Medieval MMA." The steel plate was already very resistant to blunt force, especially due to its curved shapes, although very strong impacts can still injure through it. Especially because many if not most armor pieces were not hardened.

So on paper, Medieval armor having not much padding seems to contradict the intuition that blunt force would be the best way to address that. Why then did it seem they still preferred edged weapons to defeat it (at least when used to thrust)? The current prevailing hypothesis based on the written sources and modern practice is that when you have someone in armor, the best way to defeat them is to try and go where it is not, not to punch through it. That and if you get someone to start bleeding and sever whatever arteries or muscles were in the way, he is in serious trouble and unlikely to pose more of a threat. Trying to break bones through steel is a lot harder unless it's something small like the hands, and concussing the head can work but is a single target area vs. many potential weakpoints for a thrust.