According to a new report, Samsung has chosen One UI for its next flagship smartwatches. The Galaxy Watch 4 and Watch Active 4 will run a form of One UI 3, albeit one based on Wear OS.
https://www.notebookcheck.net/Samsung-Galaxy-Watch-4-and-Galaxy-Watch-Active-4-series-to-run-Wear-OS-with-a-One-UI-twist.539825.0.html
Seems like Samsung is in damage control mode now; but however you paint it, it is WearOS inside. And that's a big no no, never ever. Very happy with my Watch3 and will keep it for a long long time.