When your wrists are bent there's less room for internal movement. The same site has some illustrations showing how the think keyboard trays should be oriented

When your wrists are bent there's less room for internal movement. The same site has some illustrations showing how the think keyboard trays should be oriented, and they have straight wrists: https://ergo.human.cornell.edu/AHTutorials/typingposture.html https://ergo.human.cornell.edu/AHTutorials/typingposture.htm.... (I don't like the page that much, since it doesn't show what I think is the best option: a flat keyboard with elbows at 90 and wrists straight, which you can achieve either with a sufficiently low desk, which I do, or a flat keyboard tray under a higher desk.)