Pedantic, but this was never a tagline. This was an impromptu interview comment along the lines of meaning "this is currently the newest/latest version of windows" but worded poorly. It's not clear they ever meant for this to be construed this way as there were never any marketing materials put out to support that interview comment.

Interesting, I always thought their strategy back then was basically to switch Windows to an "evergreen app" like Chrome where the "real" versions are service pack revisions but the "branding" version would always stay the same. Then at some point, the strategy was abandoned and the traditional "a new Windows every few years" model was re-established.