Mixed refresh rates do not work because X technically is not doing multi monitor. Both monitors are rendered from the same "screen" that uses one refresh rate. If it's running at 144hz, the 60 fps screen gets frame pacing issues. If it runs at 60, then the 144hz monitor is slow and gets frame pacing issues, and from most anecdotes and videos I've seen, it's usually the latter and a pain to fix. If you wanted perfect frame pacing on both, you'd have to have the X11 screen set to 8640hz, which I don't even think can render on modern systems. Wayland, on the other hand, just has multi monitor support built in and actively used. Each display has its own screen and renders at its preferred refresh rate, giving perfect frame rates and frame times for both.
Variable refresh rate has become the de facto standard of modern gaming now. They aren't referring to the direct draw API, but the fact that Wayland does not have extra baggage to draw to the screen through a display server. Wayland just draws to the screen directly, saving time and performance.
You're not wrong but also misinterpreting this. Yes, it's bad to push incomplete software on end users, and it's even apart of the entire development ideals of Linux: never break userspace. There's even small bits of code (see: egrep and fgrep) in the core commands that has been on the chopping block for removal for 2 decades but hasn't because removing them would break apps.
The choice of PUSHING Wayland on end users is not up to the developers making wayland, it's up to the distro maintainers, and this image honestly doesn't even make sense. Most distros right now are either so nothing, and the ones that do are disabling Wayland until it's more feature complete. The only big distro I remember that's specifically is pushing for it is Fedora, and Fedora is specifically known for pushing for new initiatives.
X11 works just fine, and will work just fine for a long time, and if there's ever a point where a majority of apps start dropping X11 support for Wayland, it's going to be because Wayland just works by that point and has for long enough for devs to care.
That article itself against has been a pain point for years because it over-dramaticises a lot of the pain points about Wayland and a lot of the issues it touts don't... exist anymore. I've used lots of software like OBS on Wayland just fine a long time ago even though the article says it's been broken for years. Nvidia on Wayland has also just gotten to a good state on proprietary drivers while the article implies you need the crappy open source drivers to use Wayland at all, which hasn't been true for a very long time. I could go on about this article, but Brodie Robertson has already talked it to death on YouTube.
Wayland does "just work" (no bugs, no configuration, just switch to it and nothing breaks) for a lot of users at this point, and I'm tired of this article ignoring that and trying to make it seem like Wayland is this buggy slop everyone's being forcefed when it's not.
If you're using the latest Nvidia drivers, try it out. I heard support improved dramatically with the latest releases.