It was a loaded question. I think the "blurring" of the 2 genres you mentioned is a matter of readers/viewers/marketers doing the blurring, not the authors.
Bradbury considers himself a fantasy writer: . "I've only done one science fiction book and that's Fahrenheit 451, based on reality. Science fiction is a depiction of the real. Fantasy is a depiction of the unreal. So Martian Chronicles is not science fiction, it's fantasy. It couldn't happen, you see? That's the reason it's going to be around a long time—because it's a Greek myth, and myths have staying power."
I've been a fan of both forms for 50 years and I think most of the writers would agree with Bradbury's definition. Marketers like the Sy Fy Channel have twisted definitons beyond logic. To them horror, corny science fantasy, gory slasher junk etc. all qualify as "Sci Fi" (sorry, it's been dumbed-down to Sy Fy).
As to the matter of Jewishness, I agree with you. But as I read it the author seemed to be referring to fiction from a mainly religious perspective, i.e. Lewis and Tolkien. It's an interesting question. Ellison's Jewish but he's sure as hell not very religiously-oriented.
“Fahrenheit 451” was the only Bradbury piece I could think of, offhand, so I’m hardly the best example for your thesis on that.
I would suggest a further distinction the author of this piece didn’t make very clear. When he refers to to “fantasy” I believe he is referring primarily to “epic fantasy,” a very specific form of which Lord of the Rings is the classic example.
Science fiction, to the extent the term means anything, refers to attempts to extrapolate into the future the consequences of potential technology based on what we presently know of science.
Fantasy as such is a much broader grouping than either epic fantasy or science fiction and is roughly the same as “speculative fiction,” which asks the questions “what if?” with absolutely no limits.
Anything goes in fantasy as such, whereas science fiction and epic fantasy are both inherently more limited. A big problem is blurring of these categories. I have no problem with “science fiction” that violates our present scientific knowledge, for instance, as long as it is at least possible that the story is set in another universe with different laws of nature. When it is clearly set in the future of our universe, but science is just ignored, it doesn’t work for me.
Fantasy doesn’t have that problem, as it is usually clearly set in another universe where our laws of nature don’t apply.