"Either they were in touch and borrowing from each other...or they were not. You can't have it both ways."

You missed the bit where FR said WHEN they met the Chinese. They didn't know each other from the starts of their civilisations, therefore no contradiction.

For many hundred years they did not know about each other so they evolved independently, and then when they discovered each other they fought each other for many more hundred years and took ideas from each other - most of the developments of that time were gained from wars. The stirrup, a Chinese invention, was poached by the Japanese, for example, because it was a good idea for cavalry, making fighting from horseback less problematic.

"All governments suffer a recurring problem - power attracts pathological personalities. It is not power that corrupts, but that power is a magnet to the corruptible" - Dune, Missionaria Protectiva.