At least some of the GB boats were built without the structural support prior boats were built with. The Sunfish class was surprised to say the least. I am looking forward to finding out where the medallists boats were made.
The following is mostly speculation!
Yes, current (2019) Sunfishes have GB (followed by a code) on the stern. Some have speculated that the hulls are built in China and the fittings put on in the LP facility in England. But it is fairly certain that these boats don't have the internal (vertical) foam panels anymore that connect the deck to the bottom. So we speculate that they will flex more in waves. I have no idea whether this was relevant during the PanAm racing on the Bay of Paracas. It would be super if we could get a report from Conner Blouin himself, but I don't think he reads this Forum.
I also don't know what vintage Sunfish the other sailors were using.
TracTrac didn't play nice on my computer yesterday, but today (8/11) I was able to watch the whole race. The course was windward/leeward (gate)/windward/leeward (same gate) and a short reach to the finish. Apparently, the wind was light (~7 knots).
At the first mark PER
First time at the gate
Second time at the windward mark (no change for the leaders)
and at the gate for the second time
Blouin had overtaken Ramsay, and that's how it ended
Very briefly, PER took the lead early on and was never threatened. The rest of the fleet was closer, except for GUA who fell behind by a lot right after the first mark.