A congested area has no route in or out that doesn't involve overflying property .
If a town/city was in a U shape , you could fly right into the centre of the U as it wouldn't involve overflying property ..a bit like the route to City Airport from the North . A rugby pitch or golf course in itself cannot be a congested area , but it could be landlocked inside a congested area . You need to look at the reason for the rule . It is all to do with having a safe landing spot in the event of engine failure on approach or landing . That is how I have decided over 30 years and never had any problems !!