Like the Back of My Hand

In the more than four decades I've been involved in the hobby of roleplaying, I've played a lot of different games – and spent a lot of time exploring the settings associated with those games. I was reminded of this during the past week, because I'm going to be playing in a new Traveller campaign set in the universe of GDW's Third Imperium. As I was generating my character, I very quickly found myself imagining who he is and how he fits into the larger setting of the game. Indeed, it was quite easy for me to view the results of my random rolls through the lens of the setting of the Third Imperium and this, in turn, provided me with additional ideas about my character's history and personality. For example, the fact that he has a low Social Standing score and was repeatedly passed over for commissioning as an officer in the Imperial Navy suggested to me that he might have a grudge against the hidebound aristocracy of the Imperium. Of course, the rolls themselves suggested very little of this; I was simply interpreting them in this way because of my deep knowledge of the Third Imperium setting.
Later, I marveled a bit at this. I do know a great about the Third Imperium, having been a fan of Traveller since 1983. I was also heavily involved in Traveller fandom in the '90s, which eventually led to my writing for Traveller: The New Era and GURPS Traveller. Consequently, it makes a great deal of sense that I should know the setting as well as I do. At the same time, there's a certain sense in which this is profoundly weird. Knowing the minutiae of a wholly imaginary place is a peculiar kind of knowledge. It'd be one thing if I were ramble on at length about the Napoleonic Wars, the suppression of the monasteries under Henry VIII, or the Russian Civil War, but it's wholly another if I do the same about the Interstellar Wars, the Psionic Suppressions, or the Imperial Civil War. I'm not suggesting there's anything wrong with knowing so much about a fictional setting, only that I can't help but find it a little odd.
Of course, Traveller's Third Imperium isn't the only fictional setting about which I know a great deal. I also know a great deal about Tékumel, knowledge gained in no small part due to my refereeing a longstanding campaign in the setting, not to mention producing a well regarded fanzine about it. Just like the Third Imperium, I can talk at length about the intricacies of this imaginary planet, including its history and inhabitants – and do so with a confidence that might suggest, to the uninitiated, that I was talking about a real place rather than a fictitious one. That's a testament to the power of the imagination, to be sure, but, as I said above, it's also more than a little weird.
Am I alone in thinking this? For that matter, does anyone else possess a similarly high degree of knowledge about an imaginary place, particularly one designed for roleplaying games? I assume there must be, for example, Glorantha-philes who know as much about that setting as I do about Tékumel, but what about other RPG settings? I'd be very curious to hear what others have to say on this topic, as it's been on my mind quite a bit lately.