latest news posted on rog forum
I called Asus support the night before last and the agent told me they were receiving many escalations regarding this 2080 issue and their engineering team is currently working on resolution. The only information they could provide me was it is indeed related to nvlink interface incompatibility with current BIOS/board, and users of the 20xx series GPU's, whether multipgpu or single gpu may face issues and instability until BIOS update is released.
They also stated there is other issues related to the 20xx series GPU's and screens going black prior to login screen in windows/drive instability with boards at the moment, and this is affecting other boards as well (not just the ZE) and they are working on BIOS updates for these issues too.
They said to expect BIOS updates "soon" and their L2 teams will keep in touch.
Seems the NVlink interface, regardless of multigpu or single, is causing issues with ASUS mobos in general for many. I suspect they never really added support for it since it was technically outside the scope of the market these boards were intended for (well, until now).