No.  The link is about the overhead of having to use X *at all*, instead of being able to use Wayland directly. Either because they don't know how to grant access to Wayland for the container, or because the want to run the same containers that rely on X; it's not really clear.  There is no way to avoid this overhead if you have X support as an explicit requirement!

The lower-overhead *and* secure way to implement your goal would be to drop X and use native Wayland with no translation layers. Flatpak app containers are implemented using Wayland for this reason.  AFAIK they do not attempt to provide any Qubes-like features when X is used.