i was wrong in my posts above,
they do all work on all the USB controllers. However, there is a timing/init problem or some kind where they dont always work each time they're connected. they do work after two or more reconnects. this problem does seem to be unique to the Boom devices, as nothing else i've tried has this (and i've tried many other kinds of adapter).
another issue i can confirm: some are more picky about N64 controllers than others. about half the adapters i get work with some original N64 pads i have, and half don't. other controllers work on all of them, its definately a bug with the adapter.