In a perfect world, we would offer both and a choice between X11 and Wayland when a desktop is installed via dietpi-software. But our developer man power is simply too low to start tinkering with this, and there are higher priority tasks keeping us busy.
We are open for PRs/contributions about this. But it is 5 desktop installations which would need to be made functional with it on a range of different platforms, so probably pitfalls to expect.