If you used --help, then decided to pipe it to less, and it disappeared, then you can't have been confused for too long. But agreed that an explicit --help should print to stdout.

However, if you used the tool incorrectly (passed the wrong args) and you expected the usage information to go to stdout rather than stderr, I would disagree vehemently. stdout is (generally) for parseable information, whereas stderr is kind of a garbage bin of everything else.