These are great questions. There are clarifications on some of them, and this collection is a reference I turn to often:
On some of these, you simply have to use your best judgement. A blanket statement can’t cover it.
For example, tree markers. If the marker is a destination along a tour through the arboretum, I think it does qualify as a unique point of interest for exploration. If the arboretum has simply put a label on each tree, my personal opinion is that it does not. But I often see these submitted and accepted.
We would be glad to give opinions on individual submissions you see in review.