I don't get why they specify that it's not actually a henge, since a henge is "a prehistoric monument consisting of a circle of stone or wooden uprights" and "d

I don't get why they specify that it's not actually a henge, since a henge is "a prehistoric monument consisting of a circle of stone or wooden uprights" and "dating from around 3000 BC to 2000 BC, during the Neolithic (also known as the new Stone Age) and early Bronze Age." I suppose it's out of scope for the article to dive that deep, but it would be nice to know the difference between this site and a henge. The water is after-the-fact, so it can't be that.