The challenges last night were reversed! The fishing challenge SHOULD have been reward while the fire should have been immunity. I'm sure that's how MB originally planned it. I cannot think of any other immunity challenge where the winners won something (FISH) aside from immunity. It was a reward challenge!
And of course, the fire challenge should have been immunity. Fire is life, blah blah blah.
What MB did was see an opportunity to give the men a slam-dunk immunity win (seeing they were much better fishermen) and even up the tribes. So he simply swapped the challenges!
IMHO....