why are dark age buildings universally represented by wood and hide structures when this is almost certainly anachronistic to all depicted civilizations?

disclaimer: NOT a professional historian, please forgive any inaccuracies the ‘dark ages’ in europe is commonly (and erroneously) understood to be an era where much of the knowledge of the roman empire was completely lost, resetting european civilization to a ‘dark age’ where many technological advances had to be re-discovered. this pop-historical understanding of the post-roman empire landscape is almost completely overblown, something the aoe II team should have understood based on how much research they would have had to do to form the civilizations and their unique bonuses and identities in the first place. furthermore, if this information collapse did result in a reversion to simple wooden structures, it would not extend to civilizations outside of europe. even nomadic civilizations would likely present differently, given the collapsable nature of their structures, making anything other than very thin wood frames impractical. so what reason is there, gameplay-wise or any other, that all civilizations are depicted with a uniform and overly simplistic architecture in the dark age?