It's simply length. Ethernet is expected to work on 50-100m runs, while USB4 specifies maximum cable lengths of 2m even for just 5gbps (at least for passive cab

It's simply length. Ethernet is expected to work on 50-100m runs, while USB4 specifies maximum cable lengths of 2m even for just 5gbps (at least for passive cables). 80gbps is 0.8m