Why do the first and third of the following conditions work, but not the second? That is, why can you write a condition about an object on a supporter (or in a container) or a person in a room, but not, apparently, about a person on a supporter?
The park is a room.
The bench is an enterable supporter in the park.
if something is on the bench:
say "Something is on the bench.";
if someone is on the bench:
say "Someone is on the bench.";
if someone is in the park:
say "Someone is in the park."
Alice is on the bench.