Okay that's definitely not the one I was thinking of. However, he reportedly wrote a story a year for Issac Asimov's periodicals for almost two decades, plus his many actual books, so it is no surprise that some of his themes were re-used, yet hard to find the name of:-).
I thought the one I am thinking of was neat b/c the dinos were gate-keeping offering their transportation technology to humanity, thinking that surely no warm-blooded mammal could possibly keep their emotions in check to do what must needs be done, unlike the cold heart & keen mind of a reptile.
In other works like his collaboration with Arthur C. Clarke "Altered Carbon", Pohl used the concept of that "stack" to limit the spread of one human mind that would otherwise just be spread out amongst the stars with as many copies as bodies could be found to hold them. But in other anthologies there were other limitations preventing that (and presumably some others still that I haven't read where those limitations were removed?:-P).
Yeah and he could also have been a clone, so both rather than either-or:-). I don't think they'd hesitate to lie to him, or conversely to tell the truth about his abduction, so if he has memories that they allowed him to keep I presume they would be real - the Vorlons just couldn't care less otherwise so why not? (Occam's Razor)
You bring up a very interesting point about Kosh: yes the Vorlons were assholes, but he (it? they?) was not - and oddly enough, it wasn't that he "wasn't a (real) Vorlon", but rather like he was a true one and all the others were the fakes?
I don't quite have the words but like, he was what he was because he knew about the ancient task that they had set out for themselves hundreds of thousands or even millions of years hence, and decided to actually do it rather than as the others all seemed to, do the exact opposite of "guide" the younger races (to self-discovery).
John Sheridan was ofc the same type, as too was G'Kar: both men ready for war, while in the service of peace (a different purpose than the Vorlons... or is it?).
We see this all over now: people showing up on January 6 at the USA capital to "defend" democracy by... overthrowing it? And religion that somehow becomes warped into diddling kids, yet side by side with others in the "exact same" religion who take care of widows and orphans and do so much good in the world. The cheaters are never going to be honest about who they are, preferring instead to hide out within the existing substance living as parasites rather than do the work of making their own structures, borrowing its reputation and forms of earned authority - e.g. President Clark did not declare himself an emperor but retained the title of a democratic "President", despite the literal coup that gave him that position.
Kosh, John, and G'Kar were those who refused to blindly follow their culture to "just do the thing", and instead questioned everything according to the logical principles of self-consistency: "is what I'm doing right according to the goal that I want to eventually reach?", and by doing such they not only served their peoples (hehe, but not necessarily the ones in charge at the time) but also lead them, as in they went out ahead and did that next right thing, thus setting an example for others to follow, if they wanted.
So I said that I lacked the words but a stab at it could be: Kosh was who he was not despite being a Vorlon, but rather because of it. However, if true, that has massive implications for the nature of Truth, i.e. it must not be defined by a majority-rules consensus (even for something like a race of people or a democracy) and rather some other standard that if not purely external then at least is not entirely internally defined, in the sense that it is a combination of whatever was internal but also subject to the (external?) constraints imposed by the need to remain logically consistent.
As in, there was a "correct" way to be, and Kosh chose it in defiance of his people, which we as consumers of the media recognize and respect.
That show is so deep. Or perhaps it is better to say that I feel deeper as a result of thinking about the material presented in the show.:-)