Oh I think I understand your question. I say those are HDR reflections because they are reflections of HDR data. Look at my last image.

The flat mirror and the black sphere are reflecting the same thing, but at different exposure levels. If the e-sphere image was not high dynamic range, then the part that looks white (outdoors) would actually be clipped at white. A reduced intensity reflection of that such as on the sphere would be a solid gray. Instead the reduced intensity has detail in it - detail we could not see at the exposure level reproduced by the mirror.

A low dynamic range image would not simultaneously have meaningful interior and exterior detail. You'd have to choose which to record, by chosing an exposure level. That would lock in the data for one range and totally discard the data from the other range. So low-intensity reflections and high-intensity direct viewing would not be simultaneously possible as it is in my render.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)