[markonen]

It's 8×100G yeah, but they also use two fiber pairs so four lanes go on each.

The QSFP-DD modules are also bigger (they stick out further from the slot) and have more power available, so that probably helps somewhat with engineering.

[MichaelZuo]

It's incredible how advanced the technology is, that fully saturates PCIE5.0 x16. but at a distance 1 million times farther.