When a forest is small enough, it is not a forest. As my Irish mother would say, it a “a wood”, which, I guess is the singular form of “woods” for a group of trees. Ireland, the whole island, could get lost in the Brazilian rain forest or the forests of the Pacific Northwest of North America. To call a couple square miles of trees “a forest” is an exaggeration. Winnie the Pooh lived in “The Hundred Acre Wood”.
Beara Rainforest is a 32-acre tangle of old Sessile Oak
32 acres < 100 acres. It’s a “wood”, not really a “forest”. ( I’m joking, your link is interesting and informative. I wish there were more oaks planted in Ireland, not the quick growing pines destined for pulp mills.)
Forest just means (former) royal hunting ground in Britain.
Britain is also the land of villages with over 30,000 population, towns with over 1,000,000 and cities with 1,600 people living there. It all makes sense, honest.
(Ireland has similar rules because the British monarchy and government are imperialist bastards)