"The pointing finger is not the moon" has never, IME, been taken to make ontological claims of any kind about the moon, except that it's not the finger pointed at it. It means the same thing as, "The map is not the territory," and not, "Because this map shows rivers and towns in these locations, such rivers and towns must exist."
Your idea of a thing is simply and solely your idea of the thing; the thing, itself, is simply and solely the thing, itself. Buddhism just suggests out that you conflate them at your peril (to the extent, of course, that Buddhism has a notion of "peril").
Einstein: The moon is there whether or not anyone is looking at it.
Heisenberg: The moon may not be there if there isn't anyone looking at it.
Buddhism: The hand pointing to the moon is not the moon.