freebeer
Most likely they are imported as NHD objects, like the TIGER street import, before additional uses were conceived beyond the raw barebones data, back in the baby steps of OSM.
In many cases the NHD data is no longer current, as development takes over, or it no longer meets the standards OSM expects.
As you deleted this object, I can\t see its history without firing up an editor (well, I could, but I hate learning) but the one south of here is indeed imported.
By now I get suspicious of every little or big park-like thing I see, especially with osm-carto now rendering them as a nauseating fluorescent lime-green.  But that's probably because of all the vandalism I'm following.