"Security through obscurity" is the vernacular formulation of https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle and refers to using bespoke encryption algorithms rather than strong encryption keys. I don't see how it has any bearing here.
Indeed, outside of cryptography, keeping substantive knowledge secret is quite often a critical component of security. See generally Rogue One ;-)
Well, the "security though obscurity" principle has been used for many years now to cover alleged extra protections granted by the mere fact of keeping a software source code closed and secret. As in: you will not find that RCE in the software if you don't have access to the source code. And this statement from Dell and the FreeBSD foundation (yeah, it's not just Dell) clearly follows that line of thought.
That is simply a mistaken understanding. Keeping source code closed is obviously a legitimate form of security if the source code itself contains proprietary trade secrets (such as hardware details).
No reasonable person could disagree; the proposition is so self-evident it's virtually tautological.
Well, language and meanings evolve over time and you cannot control how they do it.
Also, how protecting trade secrets via closed source "creates a robust platform less susceptible to attacks than a CopyLeft-based system with GPL components."?
Does keeping the source code for the Death Star exhaust port controller firmware secret help create a robust planet destroyer less susceptible to attacks?
Indeed, outside of cryptography, keeping substantive knowledge secret is quite often a critical component of security. See generally Rogue One ;-)