if licensee claims ownership of the work in any form
Your clause wouldn't work since it was Epic's parent company that made the ownership claim. You would need to put something nice and broad in there about parent companies, partners, or affiliates. I'm sure a lawyer would know exactly how to close that loophole.
Why is this argument not used against X11?
Because Wayland is being written with a clean, modular design that doesn't attempt to tightly couple a bunch of unrelated nonsense into it to create a complicated mess. Because Wayland is being written primarily by former X developers who have pushed X to its limits but have no choice but to start from the ground up to get modern features such as tear-free drawing. Because Wayland is capable of running X applications thanks to a compatibility layer. I'm sure there are plenty of other reasons that escape me, but these are just a few off of the top of my head.
It would be absolutely fantastic if people would be rational about tech news.
With the amount of fearmongering that goes on in the media, it would be great if people would be rational about ALL news. With that said, I can't help but think that in some cases the reason that the proposed regulation isn't as bad as people fear is because the fearful raise some reasonable objections and the government scales back the scope of the new regulations. Therefore, a little paranoia (and more importantly, voicing your concern to the government) can be good at limiting the scope of proposed regulations.
"Consider a spherical bear, in simple harmonic motion..." -- Professor in the UCB physics department