How does that have anything to do with disabilities? Honest, it sounds like a form of fancy customisation and I don't doubt Wayland may not support it, but that's not why accessibility is a thing.
Accessibility is customization, and customization is accessibility. They are one and the same.
User control over interfaces is an accessibility feature. At the heart of accessible control schemes is the notion that if a user isn't able to use a traditional control-scheme they should be able to build or hook into something else or customize something that works for them.
This is a big problem with how the Linux community thinks about accessibility. Accessibility is not a separate concern from user agency and control. Accessibility IS user agency and control over a user's interface. It is the ability to take an interface you can't use or that is frustrating or painful to use and to adapt it to your needs.
Accessibility is fully aligned with Linux/GNU philosophy, but we treat it like a separate issue and like it's a chore to support, rather than being a central pillar of how we ought to be approaching software development in general.
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Here, GP has RSI which means their customization is linked to a traditional physical disability. But to be clear, even if that wasn't the case and even if this just made their life easier and they didn't have a clear, socially accepted disability classification to point to -- customization is still accessibility. Gatekeeping accessibility or asking people to prove that they're fully "disabled" isn't really helpful, we should still be prioritizing making it possible to build things like this. And we should still be treating it like an accessibility concern regardless of whether there's an easily defined disability to point to.
I have solved this by replacing my keyboard with voice commands almost entirely (I don't actually have a keyboard on my desk, but I can reach for my laptop keyboard if I really really have to), and am slowly working on replacing a trackball with an eye tracker (it's kind of headache-inducing though, so it's likely the trackball will stay for a while)
I'm not a medical professional but that sounds like a disability to me.
When I hear accessibility I tend to think of screen readers - magnification or text to speech - for people with low vision.
Real diseases often have a progression of permanent damage over time and real treatments have positive and negative interactions with other aspects of patient health, cost, and a wide range of outcomes. Commercials especially push a simplistic view that a person has a problem and undergoes a treatment and their problem is resolved. This is as real as crimes being solved in scope of an hour drama or as real if you prefer as people hacking by pounding on the keyboard really fast.
Most users in Developed countries have access to both doctors and the internet and have whatever level of problems they have in spite of pursuing treatment options and probably wont benefit from "one weird trick" to beat RSI.
The odds are pretty good that computer-related RSI is similar to other computer-related RSI. I see no particular need to specify that I'm not talking about tennis elbow when that is already abundantly evident from the context. Most of my comments could include an accurate disclaimer that I'm not talking about tennis elbow, but it wouldn't improve any of them.
Only on the internet would someone discuss a change they've made due to a disability, only to have someone else say challenge them on it and imply that they're bullshitting.