Gaffer Tape said:

Forgive me for my ignorance (as I've never seen 2001), but I admit I fail to see how taking the time and money to shoot "miles" of unnecessary special effects footage would produce any kind of tangible benefit over simply storyboarding them out and producing what footage needed to exist.

I only know what I read in the old making of 2001 paperback, which is probably still out of print twenty years after I found a copy in a used bookshop. They were breaking new ground, so there probably was a lot of filmed tests in any case.

The author could have embellished things though.

Douglas Trumbull was working on making a 2001 documentary, but either Warner Bros. or the Kubrick estate pulled the plug. :/