BB didn't react to anything. Dude barely lifted hands as the last means of defense and still got slapped back along with Van. It's fine, BB's generally careless. It's not really an anti-feat for him. You're getting unnecessarily way too defensive about it trying to make it look like an impressive feat when it's not. There's no comparison b/w a dying WB and prime BB. It's a shame that you're even making such comparisons.
What you need to look at to determine the difficulty first and foremost isn't the state of the island but the state of the characters fighting in it, then comes everything else.