Interesting!

https://github.com/WebAssembly/multi-memory/blob/main/propos...

The scaling point is what I was thinking of.

"As long as Wasm memories are limited to 32 bit address space, there is no way to scale out of 4 GB memory efficiently. Multiple memories at least provide an efficient workaround until 64 bit memories become available (which may still take a while)."

So pretty similar to launching several processes on 32 bit NT or Linux, each having their own memory space.