The apps probably run in XWayland just like any other X apps. The Window Manager is trickier but apparently XWayland has recently gained support for running a full X root so technically yes:
Huh, that’s pretty neat! But it’s not able to manage Wayland applications, is it? From the Phoronix post it almost sounds like this might be really intended run X desktops on systems that can only use Wayland?
https://www.phoronix.com/news/XWayland-Rootfull-Desktop