Well, yes, but I mean it's just this name, floating out there in space. The tiefling empire, somewhere in the past of this world with no map, that we know almost nothing about, except something regarding the dragonborn empire. There's no context to it so it doesn't seem real.
I think either nothing (just an implied setting with no specific world) or the whole hog (here's WHFRP's Old World, and it takes place HERE), or at least a sample world (Rules Cyclopedia's Mystara chapter, which at least has a MAP) would have been better.
I mean, I'm used to envisaging D&D worlds. Without a map or a name, and instead just some motherhood statements about the nature of the world, plus a couple of empires floating somewhere in the past, I think newcomers are going to quite rightfully question this thing's existence.
I know I sure did. I never had that problem with FR, GH, DL, DS, KW...they all made me want to believe.