It’s a balance of probabilities.
Not one Xen screenshot was leaked.
They were giving the game to various, almost random if Ram is to be believed, people to playtest.
Lots of other things were leaked.
So, either the xen is not started yet/barely started yet.
Or, they didn’t include it into any playtesting versions.
But if they didn’t include it into testing versions, then it’s likely that it is not worth being playtested yet.
Which suggests that it’s in early stages of development.
If it is done enough to be worth a playtesting, then there is no conceivable reason to keep it from the testers.
So, in decreasing likehood:
-Xen is only started on.
-Xen is being near finishing, but still too buggy to play.
-They have been lucky with the leaks/Xen is only recently approached playworthy state - no time for leaks yet.
-Devs have a devious plan i have not considered.