@DanT thanks DanT. We have vectorworks 2020 landmark edition in the office. I investigated it's SCI function yesterday and it looks like it hasn't progressed any since you looked at it.
The SCI fun croon seems to be just a simple vectorscript which inserted a light source at a nominated height. For some reason, when I placed it on a test terrain, it also shone "through" the terrain to hit other facing terrain planes...!?!
This isn't something substantial enough to add to a report and be able to quantify effects in any meaningful way.
I appreciate that you got back to me and wish you all the best.