Edit rejected for not making post accurate; it does

I am a fairly new user to Stack Overflow, so forgive me if this is too specific to be posted on meta. If it is, I'll gladly remove it.

I recently made a fairly small edit to an answer since it inaccurately said that base64 encoding uses only alphanumeric characters, when it also uses '+', '/', and '=':

base64 encoding takes 8-bit binary byte data and encodes it using only the characters A-Z, a-z and 0-9, so it...

This is a fairly small error, but is objectively incorrect and could cause users to leave with false information about base64 encoding. I edited it just to make it correct so we wouldn't be putting incorrect information out there.

It was rejected with the reason: "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."

I think it does clearly make the post more accurate. I ended up answering the question myself, but it seems like an edit really should have been all that was needed to ensure the current accepted answer (which will likely remain that way) was more accurate.

To the point:

• Is this a reasonable channel to express this thinking? (I figured posting here on the meta would make sense but I don't know if this site is meant to be more general rather than specific cases)
• Does my reasoning make sense, or have I misunderstood something about the process of editing existing answers?