I imagine that BMW couldn't increase displacement & HP any further under the opposed-twin design with oil cooling. Hence, the Wethead.
Without getting into the other pro's & con's of the new design, I trust that those more-exposed headers are resistant to corrosion. My old Suzuki GSX-1100F's headers were sandblasted by debris throw up from the front tire. I ended up having them treated by Jet Hot to remove the corrosion.