Within a single physical system ("multi-core multi-CPU" or with NVMe) - you rarely use something like rsync, zysnc or keysync: Your files are already local, on your system. If you want a second copy of a file on the same system, you would symlink or hard-link, or use other filesystem mechanisms. It's not even clear a clean copy would be slower than doing a bunch of comparisons.
On the other hand, between remote systems, the "modern day architecture features" mostly don't apply. I suppose a more clever use of modern kernels could help performance somewhat. Maybe.
Within a single physical system ("multi-core multi-CPU" or with NVMe) - you rarely use something like rsync, zysnc or keysync: Your files are already local, on your system. If you want a second copy of a file on the same system, you would symlink or hard-link, or use other filesystem mechanisms. It's not even clear a clean copy would be slower than doing a bunch of comparisons.
On the other hand, between remote systems, the "modern day architecture features" mostly don't apply. I suppose a more clever use of modern kernels could help performance somewhat. Maybe.