Single player commander battles? Do you mean Custom Battles, where the player takes control of an army? I presume so since the only other single player modes in native Warband are the full sandbox and the tutorial. How is that anything like a commander battle, where multiple players each control a small group of NPCs?
The AI uses formations. The infantry of both sides (which were not player controlled in the E3 battles) met without breaking formation (to fight as individuals before the lines met, which would have happened in Warband). The cavalry of both sides guarded the flanks of their respective armies and returned to those flanks in between engaging enemy cavalry. At the start of the Vlandian video, we see the enemy Imperial cavalry approach the player cavalry on the player army's left flank. They fight, and whilst they do so the player team's infantry continues onwards towards the enemy army, though the xbowmen stay behind to fire on the enemy cav. This is a clear difference to Warband, where the enemy cav would have headed for the largest and nearest group of targets and would have gone straight at the infantry. All the player team's AI would have tried to attack that cavalry.
Once the enemy cav have been seen off, the player goes back to the left flank of his army and we see enemy cavalry repositioning on the same flank, while its infantry is in a tight formation on a rise in the centre. The enemy cav then charge the player cav, while the player team infantry is attacking the enemy infantry centre.
I know that telling you all this is probably in vain, since you could easily have recognised these features yourself and, presuming you can remember what a Warband battle is like, you would already know that there are big differences. I think you are set on denigrating M&B because you erroneously see it as a competitor to KCD, or perhaps just resent people raving about M&B when you believe the combat system to be better in KCD (I reach this conclusion because medieval combat is the most obvious feature the two have in common).