Using Xwayland is using Wayland. It's entirely a moot point anyways, since Wine/Proton supports a native Wayland background these days anyhow.

There’s a gradient. For example, if I ran rootful Xwayland, ran an X11 DE inside that, and then solely used X11 software, it would technically be using Wayland but it would not be what most people are referring to when they are discussing the Wayland transition on the Linux desktop. Similarly, arguing that Wayland is being battle-tested by hundreds of thousands of gamers by citing a single-tasking gaming focused Wayland compositor that only supports X11 clients is not what most people are referring to discussing the Wayland transition either.

Wine/Proton may support a native Wayland backend but it’s not currently being used on the Steam Deck.