The reason you are experiencing these issues is because LED products are tested using absolute photometry - not relative. Unfortunately, I do not have a workaround method to suggest - but, thought it might be a little comforting to know that you're not the only one having these issues.
Furthermore, I can tell you the Autodesk knows about the issue. I work for a lighting manufacturer and noticed these issues early on while trying to build content for our customers. At that time, I sent several examples to them for review. We discussed it back and forth for several weeks trying to determine a workaround, but a viable solution could not be reached. So, last I heard they were going to look into my examples to see what they could do to try and support absolute photometry in the future - but I haven't heard back from them since.
