The story of mapping is different for every corner of the world. E.g. in the blog post there's a pic where we mapped the city approximately due to absence of satellite imagery. In this post https://www.openstreetmap.org/user/Zverik/diary/399925 it shows that some regions like Africa were nearly empty ten years ago, before the Humanitarian OSM Team lauched their operations. And in 2012 the focus was mostly on basic map features like roads and rivers, while now we're adding final building outlines.
OSM editing is usually done over satelite imagery these days, so I would imagine the old one must've been very far off in some areas.