If I am not misunderstanding, your perspective is that the window surface plays a special/authoritative role in terms of window content and other ways are secondary and are, at least conceptually, dependent on the window surface.
Fwiw we've seen cases where, on Windows, a game (Bayonetta, Dragon's Dogma) uses fullscreen window with 1px borders, thus has its window surface fullscreen but client area not, but still manages to have fullscreen D3D swapchain. The presented image was cropped (or scaled, i don't remember exactly but more likely cropped) automatically, but still didn't require to recreate the swapchain, and swapchain images were fullscreen-sized.
On Wine, and if we make the D3D/VK/GL surfaces closely follow the window surface dimensions, it requires of course to recreate the swapchain, and its images are then sized like the client area and smaller than the fullscreen dimensions. Not a big issue, things work, but as the images aren't stricly fullscreen sized it can cause some suboptimal present to occur (and in Proton we have a hack for this with gamescope to make sure the present is optimal).