It's been observed in the same way that magnetic monopoles have been observed: physical analogs have been built, but nobody has observed an actual magnetic mono

It's been observed in the same way that magnetic monopoles have been observed: physical analogs have been built, but nobody has observed an actual magnetic monopole. "Nobody has observed a magnetic monopole" is still true, even if systems that behave like quasi-monopoles have been built. My conclusion (that we can't know for sure that black holes produce Hawking radiation) only makes sense if I was talking about observing actual Hawking radiation rather than analogs, which I was.