And every UU congregation I've ever seen has pretty explicitly NOT been Xian. Not even in a watered-down way. I've watched their services online, and there's been no Christ-talk, and no sky-daddy talk at all. I think that each UU congregation has wide leeway to do its own thing, and for most, that thing does not include identifying as Xian.

"Our beliefs are diverse and inclusive. We have no shared creed. Our shared covenant is expressed through the inseparable and deeply interdependent shared values of interdependence, pluralism, justice, transformation, generosity, and equity – all centered around love. Although Unitarianism and Universalism both have origins as liberal Christian traditions, today we embrace diverse teachings from many different global religions and philosophies." -- https://www.uua.org/beliefs/what-we-believe