Never said it's a bad move, i love Rails and i love Ruby as well, it was just the first time i see a framework directly mentioned in a language changelog.
ruby-core has a history of making sure Rails does not guide the direction of Ruby the language. Most of the time, advancements to Ruby the language will always have a positive impact on Rails the framework. Sometimes these changes to Ruby the language come to light because of Rails the framework. It's a very healthy relationships between the two.