Not only are third party GPUs not supported on apple silicon, but thunderbolt has significantly more latency and lower bandwidth than 'real' PCIe implementations, even ones with similarly cut down lanes like oculink.

Apple tried before to push everything out into external PCIe enclosures and people hated it. Maybe this'll go differently this time, the Mac Studio is certainly a much more compelling offering than the trashcan Mac Pro. But I think this is still a shitty and painful situation for a lot of specific users.