I suspect the skeptic who keeps playing the 5 groundskeeper 2 copper 1 estate 1 ambassador golden deck probably still wins.
It's not clear to me what the turn (or pattern of turns) to be repeated is. Could you expand on that?
If I
ambassador you a
Copper, you can't both return 2xCopper and buy an
Estate. If you return Estate and I give you a second Copper, you suddenly have 4xCopper plus one Ambassador, which is 5 stop cards, so you're no longer guaranteed to draw all 5x
Groundskeeper, i.e. the deck is no longer (perfectly) golden.
If I play
Skulk enough times, I can luck into trashing your Ambassador with
War, I can give you differently named junk with
Plague, I can limit your draw with
Fear and
Poverty, and maybe even trash your Groundskeeper with
Locusts, thereby limiting your goldenness quite a bit.
Anyways, if you want to go for a golden deck, picking up a
Gold on the way seems like a not completely crazy idea, I think.
Couldn't the Golden Deck player, if they're ahead on points, gradually drain the Wishing Wells and Secret Caves without ruining their deck?
^^ This would be the reason why.
I would be surprised if the golden deck is better than getting thin with Ambassador and then setting up alternating Ambassador + Bridge Troll terminal plays.
If over the course of two turns you buy 3xEstate, receive two junks from their Ambassador and return two of your own, you add 3 junks on net. The non-terminal draw looks to me like it can't absorb this for more than one or two pairs-of-turns. Maybe playing
Bridge Troll every fourth or fifth turn is more sustainable and for that reason better? Or do you disagree, and if so why?