I feel like all this needless bureaucracy could've been avoided completely if Linux hadn't turned into a target for everyone to (try to) put code in. The GPL allows modification and redistribution, after all. With this patch applied, any module that imports symbols from a proprietary module is itself marked as being proprietary, denying it access to GPL-only symbols. That's starting to sound like DRM.
One of the primary advantages for authors in contributing back code is to get their features/bug fixes incorporated so that they are maintained going forward and you don't have to maintain a separate code base yourself (i.e. saving work) If you maintain your own obscure fork, you lose many of the benefits of contributing code. This is particularly true for many for-profit companies: they want to forget about any driver work they contributed the second they stop making money selling it.