https://blender.stackexchange.com/questions/46825/render-with-a-wider-dynamic-range-in-cycles-to-produce-photorealistic-looking-imwell, this one says EXR can hold quite a big value per channel, way above 1.0f, obviously. But for displaying (and encoding?) it must be compressed back to device-specific 0 - 1.0 range.Thing is, if I open exr example file in gimp 2.10 and re-export it - it retain its above 100% values. It does not do this if I do this same roundtrip via cingg. So yea, we seems to be clamping at output.
Still not sure where, may be in fader? (where fade can't be more than 100%) . May be its time to ask Lion (Adam).