Would it have been so hard to say "Boss will now respawn at 50% health when you think it's dead". What's with the cryptic wording. Not sure I would call needing to do over 100M more damage a "slight" change either.
Also evidently the color still isn't able to be seen by people without an interface add-on.
The point is to allow the mystery of the game to still be present. How fun would it be if the team just gave you the secrets to every single instance and boss? Half the fun is figuring out how the best way to handle a certain situation on your own. Community collaboration and all that.
Since this isn't a bug, it will be moved to the "Not a bug" section.