I'm not sure why you're asking this as though it is a real surprise. Since Poser 7 we can load HDR images into lights and props. If you load an HDRI onto my environment sphere and use reflection you will get HDR reflections. It's simple.

Suppose the reflectivity of a surface is 10%, or .1. Suppose you have an HDR image on the environment sphere. Suppose that some places on the HDR have a luminence value of .1 and others go to 10. The reflected luminence is 10% of that so the reflection would be 1% to 100% luminence. Which means you will see only the bright spots. What is so surprising here?

To demonstrate, I loaded an HDR image of a dark room with an open door to broad daylight. The dynamic range here is clearly evident in the reflecting balls.

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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)