Silly me. I guessed Mixer Brush. These tips all seem to work very well with the Mixer Brush, but Media would be a more likely possibility, and they do work with the standard brush just fine. It is simulating traditional painting media, though why not just say "Media" if that's it is beyond me. Be interesting to hear what Adobe says. As usual, it's impossible to find anything in Help about the presets that ship, and while I have a very vague recollection that someone once said something about them, I can't find anything under What's New, either, going as far back as CS6.