Question: Scalability given that adjacent layers must be strongly connected ?

[WillCodeCo]

Apologies for mis-using the issues system to ask a question : )

Is it still the case that each mix-node needs to maintain connections to all other mix-nodes on the adjacent layers ? This is a quote I found from the The Loopix Anonymity System paper:

Each mix node is connected only with all the mix nodes from adjacent layers

So I am just curious if there are some discussions available about the horizontal scalability of this system ? Does this really have no impact on its ability to scale to support millions of active users ? Can we have layers with 10s of thousands of nodes for example ?

Thank you !