Not sure I know which question you're asking:

1. A black box RNG is still useless despite being based on a quantum mechanism, or
2. That a quantum device will necessarily manufacture random bits.

Counterexamples to 2 are pretty straightforward (quantum computers), so I'm assuming you mean 1. I'm operating at the edge of my knowledge here (as my original mistake shows), but I think the entire point of Pironio et al's paper was that you can verify random bits obtained from an adversary, subject to the conditions:

• Bell inequality violations are observable (i.e., it's a quantum generator).
• The adversary can't predict your measurement strategy.

Am I misunderstanding something?