MP, best hand South
OK, not an elegant auction, to which South contributed, so perhaps a deserved result.
Roughly half the room replicated this auction.
Roughly the other half of the room opened the South hand 3N, North raised to 4N and South punted 6N.
The point of interest, if there is one, is that the announced definition of the 3N opener appears to be identical to the announced definition of the 3N rebid in the above sequence. If the definitions are indeed interpreted by GIB as identical then you would expect identical action by North over 3N in each case, regardless of how good is the final spot.
As an aside, I would be interested in suggestions of the best sequence that gets you to 6N on this set with confidence (and stays out of a bad 6N on others). To this end I tentatively suggest that 3N-4N-6N is not an optimal solution.