wdf That's how it used to go in typical major.minor.micro versioning systems (you'd stay under 1.0.0 until out of beta, without any voluntary 'early release'). 1.0.0 meant you had the finished product with all its originally intended features. Game updates being pretty rare before the internet was a thing, that had to be it. Sometimes there was a director's cut with extra stuff, but it didn't actually use a version number to point that out.
Nowadays with early releases and constant updates post-release being very simple to distribute, it slowly lost that meaning and got closer to software libraries that go way beyond 1.0, with it being simply a point with enough features for initial consumption.