SteamAudio - vertical distance from probes

I am testing out SteamAudio - and results are good, however when I move vertically away from the probes (currently set to 150 off the floor) - it seems like sound is no longer being reflected correctly and reverb is gone.

It looks like the range is about 129 and below and then 495 and above where the effect cuts out.

Is this expected with SteamAudio or is something wrong with my setup? What could it be?