This G37573 can't be bought anywhere except on AC's website.
I searched around and this flight should be GRU-FTE-USH-GRU. So can this ticket actually be issued? And I see that GOL doesn't have eighth freedom rights within Argentina—they don't even sell it as a cash ticket themselves. They can only issue something like FTE-USH-GRU. If it does get issued, would it actually fly?

It's best not to rush into booking this just yet—at least wait until someone confirms a ticket has actually been issued successfully or the airline gives a clear response. If the AC website shows availability but GOL doesn't have the corresponding traffic rights, the booking will likely be canceled later.