This is because Carmack doesn't really do OSS, he just does code dumps and tacks on a license ("a gift"). That's of course great and awesome and super nice, but he's not been painstakingly and thanklessly maintaining some key linux component for the last 20 years or something like that. It's an entirely different thing; he made a thing, sold it, and then when he couldn't sell more of it, gave it away. That's nice! Bu…
This sounds to me like the "No True Scotsman" argument. https://en.wikipedia.org/wiki/No_true_Scotsman I break down what you said as: "Sure, he's released code with an open-source license, but that's not real open source in the sense that matters." I happen to disagree. OSS is OSS. AGPL is OSS. MIT is Open Source. Unlicense is OSS.
He only released his software as open source when there was no more money to be made with it. The idea being that even if it is of no use for him, is could be of use to someone else. In a sense, it is crazy to think of such actions as generous when it is what everyone should have done, but since being an asshole is the rule, then breaking that rule is indeed generous.
To me, working in open source means that your work goes to open source projects right now, not 10 years later when your software is obsolete and have been amortized. The difference matters because you are actually trying to make money here, and the protection offered by the licence you picked may be important to your business model.
John Carmack is making gifts, which is nice, but he wasn't paid to make gifts, he was paid to write proprietary software, so he worked in proprietary software, not open source. On one occasion, he gave away one of his Ferraris, which is, again, nice, but that doesn't make him a car dealer.