The main complaint that I have heard with wearing a PFD while surfing is that it hangs up on the board when you try to stand up. Their justification for not having one on is that they are normally tethered to their board, and that it offers all flotation they need. Not sure if they have put one of those "PFD required" signs up close to the wave, but until they do, I think its up to people to make their own decisions on the matter.
Looking at most of the pictures on the 2imagine site (Corran Addison's blog and river surfboard site), I would say about 1/4 of the people who surf the Lachines in Montreal wear a PFD, and its a much worse swim after those waves then you see on the Colorado. Sounds like it can afford some scary downtime, but as yet no major injury from it there.
I personally would stress a helmet before a PFD in this case. Alot more chance of falling and knocking yourself out then not having enough flotation at this wave. Takes one weird wipeout and a knock on the board and you are an unhappy and unconscious swimmer. Lets just hope that it stops here and doesn't get to point of having a couple of construction workers in Carhartts and steel toed boots jumping in to body surf like happened at South Canyon a couple years ago (one guy drowned and the other barely made it to shore).
p.s. Boofing a wave ?