We know that Roshar was grown by Adonalsium himself, (https://wob.coppermind.net/events/131-general-reddit-2016/#e3952) and the patterns of the Dawncities very well can be a natural effect of the process that he used to create the landmass. It seems that the Windblades were simply part of this process. (https://wob.coppermind.net/events/358-fanx-2018/#e10715). Humanity may have searched out these places because of the added protection that they added. They might have been transformed, or affected in some other way at a latter date. Similarly they would have added the Oathgates after ect. I assume that the patterns of the cities also has a connection to the fact that the singers were the original inhabitants of Roshar, and they can hear the songs, and rhythmic patterns.