I appreciate everyone's willingness to offer thoughts on the question about, essentially, what is the commercial marketplace for purposes of the FAR's definition of COTS. I hear the term COTS used frequently, but I'm not sure it always means what people think it means. Or, as this discussion above suggests, maybe it does, if there is no precise definition that limits a CO's discretion. I realize it may not be the most interesting issue to most, but I find it fascinating when there is a concept that exists and is somewhat common, and it has consequences (e.g., exemption from some regulations) but there isn't a well-defined definition for it.
I did find a reference in the 2008 NDAA, Section 815(b), that required the Secretary of Defense "to modify the regulations of the Department of Defense on the procurement of commercial items in order to clarify that the terms 'general public' and `nongovernmental entities' in such regulations do not include the Federal Government or a State, local, or foreign government." Although that provision was specific to DoD and in a section involving weapons systems (and doesn't address commercial marketplace or COTS expressly), not sure why the general public would be one thing to one agency but a different to all others. That said, while it seems the DFARS did implement Section 815(b), Congress repealed 815(b) with the 2019 NDAA. Section 812, and so DoD removed the definition from the DFARS.
I will wait until Congress, the FAR Council, or GAO or a court defines commercial marketplace for purposes of COTS, and until then will let discretion be the rule. No need to continue the discussion on my account; again, appreciate the inputs.