^Sorry, but I'm just not so sure. Memory Alpha defines alternate universes and alternate timelines as two separate things. Alternate timelines are created via time travel within a single universe; things like, say, the mirror universe and the various universes encountered by Worf in "Parallels" exist independantly of the "primary" universe.
No, that's vernacular again. I'm speaking in terms of real physics. The whole idea of alternate realities in science fiction is pretty much based on the "Many Worlds" model of quantum mechanics. What fiction
refers to interchangeably as "alternate universes" or "alternate timelines" are based on the actual
physical concept of multiple quantum histories for the universe. Regardless of whether science fiction portrays them as arising spontaneously or being created by time travel, they're both derived from this same principle.
And if Memory Alpha claims the sort of distinction you describe, that's purely the invention of whatever anonymous person wrote that paragraph in that article on Memory Alpha. I've never heard that distinction drawn anywhere else. In fact, I would call it emphatically wrong. "Parallels" was based directly on the Many-Worlds model, on the idea that the universe is routinely, spontaneously splitting into divergent quantum histories. In Data's own words: "For any event, there is an infinite number of possible outcomes. Our choices determine which outcome will follow. But there is a theory in quantum physics that all possibilities that could happen do happen in alternate quantum realities." (Which is actually a common misinterpretation of the Everett-Wheeler Many-Worlds model; just because multiple realities may exist, that doesn't require every possible one to occur.)
Unfortunately, the script follows vernacular by using "universe" interchangeably with "quantum reality," which just creates the kind of confusion that you and that Memory Alpha contributor are subject to. In the actual, real-world
quantum theory that Data is referring to, what's happening is that our universe is branching into multiple quantum histories which do not interact with one another and can thus be treated, for practical purposes, as separate "realities." Whatever jargon may be used in a work of fiction or a Wiki based on a work of fiction, that's the actual underlying science from which the fiction is derived.