The 100G to 200G is in reference to the SerDes, where the data comes and goes from the main processor at 200G. This starts to push the electronics toward photonics.

https://www.synopsys.com/glossary/what-is-serdes.html

The modules are something different. 400G is pretty common now, and 800G is the next thing, with 1.6 and 3.2 these modules are the shiny objects that are inevitable in the future.

This is a non-techie stab at it, we'll get a better explanation from others.