I don't want to participate in a "what is SF?" debate (because once you've seen a few, you've seen them all) but one other thing to consider: When there is a fiction magazine with a particular genre of choice, there might also be some boundary areas which may not be in the strict confines of the genre, but which are likely to APPEAL to fans of that genre.
Take "Stepfathers" on Pseudopod, as an example, a comedic tale featuring Yog Sothoth. I don't think that many people would say that that story inspires terror, or even unease in them. It's silly, and funny, and doesn't try to be anything but. I would generally define the horror genre as one which is defined by the feelings it evokes, varying degrees of unease or fear. Stepfathers doesn't inspire any of these, yet I'd say it fits perfectly well at Pseudopod. Why? Because fans of horror, are more likely to be familiar with Lovecraft and the Cthulhu mythos than the general population. Much of the humor derives from familiarity with the source material.
I'd say that, even if one argues that this story is not SF itself, something similar goes for it as for Stepfathers. Fans of SF are more likely to be interested in this story than the general population because it's about a child attempting to evoke the scientific method on something she doesn't understand in order to gain a greater understanding of it.
So, even if it's not SF, I'd still say it fits perfectly well in here because of the focus of its subject material.