It was an experimental feature slapped together by pg in 2009, and has been largely forgotten about ever since. The motive then was to see if there was any difference if you filtered out newer users. There wasn't then, just as there isn't now.

Its continued existence is just a historical artefact.

As far as I can see it's not linked from anywhere in the UI, and is only occasionally referenced in comments.

Nothing to be miffed about!