First off, W4 wrote that sketch, and he's got many talents, but he's not exactly a Lovecraft-o-phile that I know of. That's AoD, five doors down and look for the slime on the doorknob.
Second, it's name recognition. True, this is a MiSTing and as such is expected to be at least slightly obscure, but on the other hand, the sketch sorta depends on the reader knowing who the hell the tentacle demon in question is. Cthulhu's got the marquee value that Yog-Sothoth lacks.
Third, keep in mind it's just a 'fic. We should all really just relax.