[lostmyoldone]

While the wording isn't particularly clear, the later remarks contrasting full-width with full-screen makes it clear that full-width in this instance does not refer to the full-width of the screen, but only that the "widest" responsible layout is used.

[dbjorge]

I don't think the article is using unclear wording; I think it is clearly arguing the exact opposite of what you're describing. I think the clearest demonstration of this is the concluding section, where the author specifically talks about using "is desktop/laptop" as a preferred alternative to breakpoints that are based on window size.