[JeremyNT]

Well, think of it as a term of art and less a description of the ground truth. We can bike shed whether it's the best description, but it's what we have.

Indeed, there are plenty of examples of similarly reductionist terms used throughout history.

For example, until recently the western world marks the era of history in which we live as existing within the reign of our Lord, Jesus Christ [0]. We have now invented a backronym to work around this unpleasant detail, but we couldn't even get so far as to switch out the letters (so as to avoid upsetting people who we know are going to keep thinking in terms of "anno domini" regardless).

There's also the related "Christendom" [1] term which was in broad usage.

[0] https://en.wikipedia.org/wiki/Anno_Domini

[1] https://en.wikipedia.org/wiki/Christendom