I wonder about borders, also. I wonder when they started guarding borders like they do today. I know there were places with minimal border control, like the U.S. before the world wars. Were there places a hundred years ago and earlier where boarders were guarded like they are today? Did they want to keep the serfs in place? Did rulers care about peasants moving back and forth? Or are modern borders, imperfect as they are, only possible at this time due to modern governments and the military resources they can dedicate to such things?
My guess is that modern borders and modern passports came about around the same time. There's no sense in requiring documentation for every person crossing a border unless a country has the wherewithal to enforce that rule.
That said, passports have been around near as long as borders, just did not have the smart chip embedded in them. Letters of recommendations or safe passage to pass a port have been around nearly as long as the notion of sovereign boundaries. It might have been a parchment with a wax seal, a ring, or a stick with a burn-mark, maybe even clay tablet, but the purpose of the "passport" is the same - passage into and across a territory controlled by another group other than the person holding the "passport" - i.e. safe passage.
Your reference last states King Henry the 5th of England had "pass porte" in the early 15th century. The Greek city states had safe-passage documents between each other way before the English. There is a bilingual "letters of recommendation" in Chinese and Tibetan from the 10th century to allow safe passage for a pilgrimage. A thing that allows a non-local to pass safely into and out of a territory. (British Library IOL Tib J 754) https://www.princeton.edu/news/2014/11/17/bringing-ancient-b...