From a common sense perspective, ZeniMax AFAIK wasn't even working on VR at this time period other than Carmack dabbling in his own "free time", so this is a pretty naked attempt for them to make the claim that anything he worked on even remotely related to games is owned by them, which I have a huge issue with (even if it is a concept that holds legal water in some states).
I'd have more sympathy for ZeniMax if they were bullish on VR and Carmack was working on an official project for them in the VR space and then left for another company, but this doesn't look like that at all, this looks like a game company owned by a lawyer trying to get a big payday on an opportunity they previously missed the boat on, using tenuous legal technicalities.