I’ve kinda sidetracked myself, working right now on making profiles from spectral sensitivity data…
However, for this endeavor, since that post I’ve learnt from @Morgan_Hardwood that it’s the D65 ColorMatrix1 that he uses to make the primary sets for camconst.json. With that, I’m not sure why dcamprof wouldn’t make a matrix ICC from a DCP without the ForwardMatrix…
I’m sorta-retired now too, so I have time to pursue all of this. Let me mess with it today/tomorrow (still configuring a new computer, need to find dcamprof and compile it), and report back.