The concept of “real fan” is flawed I think. I’ve never assembled a WH40K model or read any of the spinoff novels, to say nothing of playing the actual tabletop game, but I’d say I’m a fan of the franchise. I’ve played some of the video games (Space Marine, Mechanicus, Boltgun) and enjoyed them. I enjoy reading lore and worldbuilding stuff from wikis even if I’ve never touched the franchise itself, and my knowledge of 40k is almost exclusively from such wikis.