In the brush editor, you can pick a blending mode for a brush preset, but this doesn't seem to get saved with the brush preset. Rather, choosing one just sets the blending mode used for all brush strokes.

Did I misunderstand how this is supposed to work? Are we supposed to be able to save different blending modes for different brush presets?

That's weird, I have a few presets with specific blending modes and it's work fine.
Also there is some default presets with different modes (overlay, multiply also erase is mode too).

Are you sure you didn't locked blending mode setting or so?