It's interesting because they don't monotonically get better over time. Some of the oldest depictions are pretty good, and there's some zaniness in the middle of the timeline
This famous "skeleton" mosaic has the proportions wrong as well, even though the artist almost certainly saw some actual human skeletons, and definitely some living humans with their longer arms and smaller heads than depicted :)
https://www.thehistoryblog.com/wp-content/uploads/2016/04/Ha...