This test was poorly thought out and will yield misleading results.
It's easy for people to guess who is who just comparing the drawings, but it is obvious that the artist failed to nail most of the giant archetypes.
If the drawings were presented separately, i wouldn't guess most of them. For example, imagine you're showed drawing A first. Without seeing other drawings for comprehension, i could assign A to cloud, ice or stone giants. Then B.. storm, ice or even fire? Only when i saw C i was like "ice giant, bingo". D - what the hell is that? A half-orc, half-ogre, exceptionally ugly azer? E is obviously a hill giant because he looks like greater oligophrenia elemental. And F - gorlum?
So yeah... Just because we can use our comprehension skills to guess the giants, doesn't mean we recognize all of these depictions as iconic.