Yes, yes, I've seen you Literary Tsars issue the ukase that SF is Fantasy before. But you're still wrong. On a very simple esthetic level, you're basically claiming that a hiking trip down the Appalachian trail and a cruise to Bali are the same because they're both vacations!
But perhaps I wasn't clear enough about one thing: for SF, "supposed to be realistic" is never more than "pseudorealistic." The best pseudorealism of course is the best scientific speculation possible, but if it's nothing but science fact, it's not really SF, is it? My point was that a style that aimed to pretend to be real, to be somehow connected to this world, is not at all the same as a style that aimed to evoke magic, to create another world somewhere else away from the mundane. I don't think style is everything (some more or less redefine language itself as "style,") but ignoring this is far, far too philistine even for me.
On another level, realism says there's no such thing as magic, a proposition SF formally agrees with. (Much SF is written badly in that it subverts its own stylistic nature!) The pseudorealistic trappings are indeed often used just to help willing suspension of disbelief. Certainly the fantastic elements in fantasy are not added to assist in willing suspension of disbelief. If anything they are added to use willing suspension of disbelief against tiresome reality. Sorry, but it seems a little obtuse to miss this rather dramatic esthetic difference.
Partly you are misusing "realistic" as a synonym for "plausible." This is far too subjective to be usable. For instance, you are simply incorrect that warp drives are no more plausible than orcs. Orcs somehow live in nonexistent giant cave systems without light and without food and without fuel and without water. If you think that's as plausible as warp drive, there's something wrong with your BS detector. If it's supposed to be scientific, no matter how truly absurd it is, it's SF. And if it's supposed to be magic, it's fantasy. Everything else demands you set yourself up as THE JUDGE.
This is particuarly unfortunate because, in fact, there are quite a few SF works, including classics by H.G. Wells or Jules Verne where the pseudorealistic elements are not just another gimmick for willing suspension of disbelief. A definition of SF that reads out classic works of undoubted SF is worse than useless, it is actively misleading.