It turns out that the right answer doesn't even depend on your level of shell knowledge or on how you tend to use the shell.

I use much more complicated pipe tricks than that interactively on a daily basis, and I definitely don't think of them as "arcane". As somebody who does that, it's useful to me to know which channel the data I want to pipe are going to come out on. Which is why help, which is normal requested output, should obviously go to stdout.

Usage messages issued in response to actual user errors are different, of course.