Oh wow. It sounds like they added a special attack to keep the boss fights more close. So if you fall a bit behind in hits, you can make it back up with a monster one. I guess it does nothing for you however, if you keep getting hit after your rage meter is already full.
Edit: Actually, it says "without taking the opportunity to strike back". So maybe if you are throwing wild strikes, it cancels your rage out. So it rewards you for intentionally taking hits to build up rage, then picking the right time to strike to release your rage.