Many readers have been puzzled by the fact that Stella set the action of the book at some time in the future. (around 1950, perhaps, since the minor character Claud Hart-Harris "served in the Anglo- Nicaraguan wars of '46.") I regret that I never asked her precisely why she did this. Perhaps it was a means of giving her satirical invention a freer rein. She could exaggerate current tendencies without straining the reader's credulity. The result is that the book is quite prophetic in a number of small ways: London residential districts south of the Thames have become fashionable; there are in effect "state psychoanalysts" (i.e. available on the National Health); and one may only have to live a little longer to see air postal services and video telephones in England. Moreover, at least two writers, Daphne du Maurier and Winifred Gérin, followed Mr Mybug's example and wrote biographical studies of Bramwell Brontë. Like her idea of putting of the Baedeker stars against the purple patches to separate her parodic manner from her authentic authorial voice, setting Cold Comfort Farm in the future was a technical device which was both amusing in itself and imaginatively stimulating.
One critic has argued that Thomas Hardy counts as science fiction, in the sense, presumably, that it is about the effect of a particular social environment on the lives of its characters. One of the premises of most SF writing is that if you change the environment, you can modify people's behaviour (cf Isaac Asimov's Caves of Steel).
Cold Comfort Farm is science fiction in two senses - one, it extrapolates trends current at the time of writing into the future; and two, it assumes that modifying the environment will modify the characters. Flora Poste removes Elfine from the dark and brooding atmosphere of Cold Comfort and shows her some nice shops and tea rooms, and lo and behold, she becomes more of a suitable wife for Richard Hawk-Monitor (who otherwise would have just taken advantage of her and moved on). She moves Seth to an environment where his dark and brooding sexuality will be useful - he makes a perfect movie star. She sends Amos to preach in "one o' they Ford vans", and she succeeds in interesting Aunt Ada Doom in flying.
Also, in a way, satire and parody are similar to science fiction in that both provide an alternative way of viewing the world - they look askance at accepted mores and tropes, and offer an alternative vision. One of the most beneficial aspects of Cold Comfort Farm is that it effortlessly deflates pomposity and self-pity, and satirises many other contemporary daftnesses. Compare this with most SF novels, and you can see the parallels.