Keep all of your business logic and as much of the rest of your code as possible in platform-neutral …Something you can call into from all native platforms.

This to me is the big win of Webassembly: you can compile with gcc/Clang to target it as well. It makes the browser another “native platform”

I actually agree and chose C++ as well, but eluded that part of your quote because it could be a more general choice than just those two.