To me this seems a reasonable excerpt which is not superfluous, not harming readability. I would even say it informs users of the usage of the tag. The tag in question is the '20th century language' tag, so I added in the excerpt '1900-1999' and some added text to make it readable. In response, I seem to have received a rather standard answer, which does not tell me why this would be a bad proposal:
"This edit does not make the post even a little bit easier to read, easier to find, more accurate or more accessible. Changes are either completely superfluous or actively harm readability."
It would be very informative to properly tell users why a proposed edit is bad, otherwise they will make the same mistake (if it actually was one) again. Please provide me (and others) with this information.