On this website of translated Turkish poetry, a traditional hymn of sacrifice from a Turkish Alevi village is included in its English translation, with a note at the top signed "Ali Haydar", although the research and translation was done by Thomas McElwain. The website's front page (first link in this question) links directly to that hymn with the following description:
a part of the oral tradition, recorded by Thomas McElwain (alias Ali Haydar)
I found an original article by Thomas McElwain detailing his research into this hymn of sacrifice at the village of Sarilar (near Gaziantep) in 1989. The title is "Ritual Change in a Turkish Alevi Village", whereas the website linked above cites "Rites of Sacrifice in a Turkish Alevi Village", so I'm not sure if it's exactly the same article. Anyway there's no mention of a pseudonym Ali Haydar. I found a few other references to this pseudonym online, e.g. at Wikipedia, but nothing reliable or sourced. It feels like chasing whispers and shadows.
Did Thomas McElwain take the pseudonym Ali Haydar? When, how, and why?
Assuming yes, was it to be accepted as if he was Turkish during his research in Turkish villages? How long did he keep up that false persona? Is there anything more to this story?