There are a few existing landmarks which do more than just change scores. Mountain Pass lets you take debt. Arena lets you discard a card. There are some edge cases where this can allow you to do something different in the middle of the game (e.g. pay off debt, buy Villa, play Storyteller).
Volcano, on the other hand, does not allow you to do anything different during the game, because it only does something at the very end. I don't agree with the argument that Volcano's effect on VP is only incidental, because VP is literally the only thing Volcano can affect. So I think Volcano could count as a landmark for purposes of this contest.
That said, I'm not a fan.
I think you have worded in a better way why I like it: it affects VP (and is literally completely tied to vp-decision making)
without it actually mentioning vp, but like you said it only affects vp in one way or another, either by directly potentially trashing a province, or indirectly by trashing those cards you needed for gardens or whatever.
You don't like it. That's fair; but it's cool that it's so closely tied to vp's, without mentioning it. I see eHalcyon's point about: 'yes, it's not specific about vp', but I can only interpret this as: 'it doesn't mention vp'. Well, I think it doesn't need to mention vp to have an effect that is powerful and only influenced by vp. That's why I am not a huge fan of the 'ow, it's like gold that allows you to buy vp or not'. This can only affect vp, by the very nature of how it's designed. You will play completely different, because you can loose vp. You will make your engine completely different, because when the game ends, something radically different will happen that will only affect your vp. If it does all that, without mentioning vp specifically, isn't that a thing of beauty?
Let me ask this: is there an idea that will have such a large affect on vp
without mentioning vp, that only will affect vp creation? I can't imagine one, to be honest. Rather than denouncing this landmark, I think we should celebrate it as a stroke of pure genius.