I was curious about this also, but couldn't find an answer. The most relevant thing I learned was that WebAssembly is exposed as a global object since Node.js 8.0.0, without a runtime flag.

https://nodejs.org/api/globals.html#globals_webassembly

A list of WebAssembly features implemented by Node.js can be found here (the right most column):

https://developer.mozilla.org/en-US/docs/WebAssembly#Browser...