Lens designers never take into account the issue of presenting a curved virtual image onto a flat sensor. In addition, close focus performance is not really a parameter for wide angle lens design.
11 hours ago, Phil Rudin said:
but I do understand that Sony's goal is to make smaller, lighter, faster lenses with better image quality befitting the goal for mirrorless camera
Of course, and this is true of all camera and lens manufacturers. It should also be pointed out their goal is actually to be commercially successful! What they are not doing is designing lenses for underwater use. Any lens that works well behind a dome port is serendipitous, rather than by design.
I must confess that I am not seeing (underwater) rectilinear wide angle images produced by Sony mirrorless cameras that show good corner sharpness. Many of the images I see in reviews actually show obviously quite poor optical performance, even at online resolutions. This is not about a lens “working” underwater. Will it focus, control exposure and be sharp in the center of its frame? Undoubtedly! Will it allow for sharp corners at f/11 - no one knows yet.
It’s not about secret sauce, it is about physics!
The simple fact is that we cannot (and should not) recommend lens choices for underwater use based on specification or focal length. Some work well, others do not. Unless the lens has been used and tested underwater, any such recommendation is disingenuous. I get that we are all excited about new lenses, but please bear in mind that until someone has used it underwater (and ideally you have seen the results), you are running the risk of an expensive mistake!
It is also perhaps important to note that historically, I would venture that the majority of rectilinear wide angle lenses do not work well behind dome ports. Many very good land lenses are poor. Those that do work well have been in a significant minority.