Heavy forested; leaves still on the trees. You might not see the other hunter or he you.
I once tracked a deer. It was so thick I couldn't see my stand or see the deer at the same time. The deer was found only 50 yards from the stand.

Had a general rule in one state. If it didn't go down in your eyesight and it was still running, the last shooter claimed the deer.

Once I was hunting on the ground. A tree stand hunter put a climbing stand near me. I could hear him climbing but I couldn't see the hunter and he certainly didn't see me. I moved some fifty-seventy yards away. I got to see a buck. The tree stand hunter never saw the deer.