Interesting explanation...that was a lot to think about in what would have been a hectic few seconds. If an aircraft falls off the deck with the floats inflated I've got a hunch they'd just be ripped off on impact with the water. And with all that wind blowing over the deck, with floats inflated I've got a hunch it's more likely you'd get blown over the side. Falling off the deck, whether with floats inflated or not, will be an ugly outcome. Lucky they stayed where they ended up.
As for attempting a landing in strong winds and turbulence, I've never seen an S76 have trouble landing in conditions up to the point where it gets dangerous for the passengers to get out of the helicopter and be at risk of getting blown off the deck themselves.
Out of curiosity what is the size of that Petrobras P37 helideck, is it a 16D or bigger?