So these were all known about, but never studied/copied/read/recorded/photographed/etc. ??
(confused head-scratching)
That’s Timbuktu for ya.
They were in the process of being studied, etc, but there were a lot of them, and there weren't many researchers involved, it is, after all, at Timbuktu. Not the easiest place to get to, and certainly not a center of high tech.
/johnny