Frankly that seems a little strange to me. Was it not known as one of the most commonly used supplements in weight lifting for a long time before it was thought of as a nootropic? Just googling creatine gives all sorts of results about it being a sport supplement
Honestly, I don't know. I'm not into nootropics, just a random "fact" I was aware of (fact being this group considers it a nootropic lol). But I'll reference the reddit guide if you want to dig in yourself[0]. But I'm not sure I would expect a great answer as these types of subreddits often have an abundance of unwarranted confidence.