why? M3 Ultra already had 800 GB/s (6400 gbps) memory bandwidth
Edit: Apparently 100GB/s, so a 1.5x improvement over the M3 and a 1.25x improvement over the M4. That seems impressive if it scales to Pro, Max and Ultra.
The advantage of the unified architecture is that you can use all of the memory on the GPU. The unified memory architecture wins where your dataset exceeds the size of what you can fit in a GPU, but a high end gaming GPU is far faster if the data fits in VRAM.