However, I suspect Apple has no intention of doing this, as they are more focus on pushing Metal and reliance on macOS.
I wouldn't mind seeing PCI or GPU passthrough capabilities this in Windows 10 Pro (not just Server). With their Linux Subsystem progressing the way it is, they really have an opportunity here. Though since NVidia and CUDA are supported in Windows, maybe not as necessary as the situation on macOS.
Also I don't think they've got their driver usage right. Metal on the GPU gets different results than OpenCL. OpenCL is supposed to be the 'beta' and the results are more stable with it - and again different radically between the PlaidML devices.
We’re dealing with single precision floats for everything. FWIW, every implementation of IEE 754 floats has its own set of minor oddities and quirks.