Hey there, thanks for your feedback, yes we surely know this is not the most physically correct. However when using Lumen for arcvhiz its still all about workarounds to make it look better as it´s reflection quality is still to poor when comparing it to offline renderers where none of this hassle is needed.
Hopefully in the future lumen visual quality keeps going up as it has been doing in the last updates so these type of tricks are not needed , hope we can have real time rendering and nice and accurate reflections both together, but for now it´s a great help to remove this noise that we and many others needed to ignore everyday when working with satin materials.
Our paid training will be focused on understanding the software but also on how to tweak it enough (which currently is the hard work when working with lumen) to make it get great results to sell your interior/furniture design on your clients presentations, which is the main goal of these type of renderings.