Yes, as mentioned that info comes from another APUG poster. But I do not know his source. Might you be able to PM that poster directly to see if the chain leads back to a hard-copy reference somewhere?
Right before Calumet dropped most Zone VI products I did a "distress" purchase of items I thought might disappear. A replacement light sensor was one of those items. That sensor also matches the appearance of the factory-installed one in my original Zone VI single-tube head, as well as the one pictured in the link.
I have it currently installed in my Aristo VCL4500 dual-tube VC head. That setup is not fully functional in terms of the range of adjustments available at the timer, but it's close enough that I can procedurally work around the constraints.