I thought about doing that, but I didn’t want to add a special case in the site settings code just for default_locale and triggering the reseed manually without changing the locale can be useful in other situations as well. For example: Replacing topics with new text shipped in core like we did with the ToS a few months ago.
I did add a link to the site setting’s description:
And the wizard automatically reseeds everything when the language is changed.
I like “replace” and “refresh”… I knew “reseed” was too technical and probably isn’t even a real word, but I couldn’t think of something better. 
Yes, it’s creating a new revision.