Saturn has a tilt just a bit more than the Earth and it experiences seasons; the pole is rotated something like 26 degrees into our field of vision in "winter". Uranus is actually rotating on it's side.
The answer is we don't. Unlike the other three gas giants in the Solar System we can't see Jupiter's pole clearly. So Jupiter is unique to our solar system, and we don't know much about the visual details of exoplanets.
The thing is, there's a lot of gas, which like any other matter, has mass. So, even though a hydrogen atom is the lightest element possible, and we think of hydrogen gas a being light, that's just relative to other things. At a human scale, it isn't possible to have that much of the stuff around. But you can always go and collect a lot of it; in fact if you get ten to the power twenty seven kilograms of the stuff, and put it in one place, gravity will shape it into a sphere that looks very like Jupiter. Or, get 1000 times as much as that, and watch as gravity squeezes it so much it begins to fuse into helium at the centre - you'll have a star the size of our Sun...!
Jupiter is almost all hydrogen. However, the bulk of that hydrogen is actually liquid. Its core has compressed the hydrogen so much that it's ionized and is essentially a metal.
It's an interesting story with an awkward headline and opening quote. The word "unique" is being pressed into duty as a terse synonym for "interesting in all sorts of ways that will require you to read entire paragraphs of information to understand."
I'm inclined to forgive NASA on this one. The accuracy/brevity trade-off tortures anyone who tries to popularize science.
It's unique within our solar system, the only one we have details about. I think it's fair to state that as being unique. The implication (that we don't know about other solar systems) doesn't need to be stated, at least to me.
Since we're in the business of nitpicking – unique means one of a kind, so the "truly" is redundant. That said, there are so many planets in the Universe that it's practically impossible for any single one to be unique – the term is being used here not in a technically accurate way, but in a loose, "I want you to be impressed" sense.
Hold on -- how much do we know about the poles of gas giants in other solar systems? I'm guessing we can't get a good look or anything...
Edit: added quote to clarify what I was responding to.