Not sure how this generalises, but for video editing - less rendering, which is already fast for most workloads, but the actual tasks of editing, grading etc -

Not sure how this generalises, but for video editing - less rendering, which is already fast for most workloads, but the actual tasks of editing, grading etc - CPUs are still nowhere near fast enough. You can easily bring a modern machine to its knees realtime editing 4K or 6K H264 / H265 video with grading at native resolution. Let alone 8K video. Dedicated pipelines for decompressing various video codecs on the fly (including ProRes) are part of the reason Macbook Pros sell so well for video tasks. Another is that you can run them unplugged without slowdown, which is incredibly useful for video editors (good luck editing on a train, plane or back seat of a cab with a windows laptop). All that said, DaVinci Resolve which is increasingly taking over from Premiere for many commercial editors, is more GPU than CPU bound. Lots of sales of the current fastest GPU Nvidia's RTX 4090 to this market.