That helped but not always. alt.games.gb which used to be a group for Galactic Bloodshed got overrun by Gameboy posts at some point. And there was a time period when gnu.emacs.help got some posts related to Apple's eMac line.
Or see this post [1] about comp.windows.news, which is not about Microsoft Windows
Reddit subreddit creation form actually recommends that subreddit names should end with a suffix that describes just that e.g. kafkasoftware. The lack of enforcement of this rule caused it to become forgotten.
I mr would be unfair if this only got enforced on newer subreddits. They already have to compete with other subreddits that got easy names early on.
If all subreddits had to transition to this. Cool. Obviously that isn’t going to happen.