See those two issues:
https://github.com/ericmorand/twing/issues/284
webpack/webpack#8171
To summarize, in the current state, dist/index.es.js and dist/index.js are not exporting the same API. It means that what works when using parse-function in a node env is not guaranteed to work when using parse-function in the browser after parse-function has been bundled by WebPack or Rollup.