As it has been many times I get asked the question, put as much now about things straight: yes, there will be texts that provided SF 'they are not in the register "hard-SF" and they have significant fantasy elements and / or horror. After all, this was the case of a large part related SF stories published until the pulps as specialized Amazing Stories and his successors in the 1930s are shaping American science fiction as a genre defined with relatively precise rules.
Reissue to 750 ex. numbered in 1978 the famous "round robin" SF / Fantasy
published in 1935 Fantasy Magazine (USA) in September 1935. Ex # 233.
(click on image to enlarge)
So little chance to read for example of Space Opera Wendigo will be, to make a comparison distinctly American, more under the sign of Weird Tales, Argosy or Adventure than under that of Astounding ... But other issues closely associated with science fiction like the invasion from elsewhere when it is treated as was done in Lovecraft "The Colour Out of Space", and not big shot death rays and spacecraft, will be quite a place in the magazine. Same thing for the planet Mars when it is "perfect" on Edgar Rice Burroughs or the lost civilizations of the Lost Race novels, etc..
RDN