BoxGeometry was once replaced by BoxBufferGeometry, (thus BoxGeometry was deprecated) then BoxBufferGeometry replaced BoxGeometry, and BoxBufferGeometry was deprecated, and BoxGeometry was replaced by BoxBufferGeometry, and un-deprecated. It was a weird time. We have scars.
Now we pretend like the original Geometry class never existed, but it still pops up now and then like a zombie.
There’s good information in the docs, but they are getting pretty creaky. The search is weird/busted in the examples, and in the API docs. They really need some modernization / love.