Third party modules don't get transpiled by preset-env

[fgnass]

🐛 bug report

The parcel documentation states that dependencies in node_modules get transpiled using preset-env but this does not seem to be the case.

🎛 Configuration (.babelrc, package.json, cli command)

Here is a minimal repository to reproduce the issue:
https://github.com/fgnass/parcel-issue

🤔 Expected Behavior

Parcel should run files imported from node_modules through babel with preset-env, leaving no ES6 code behind.

😯 Current Behavior

The spread operator in /index.js gets transpiled, the one in node_modules/third-party-test/index.js is left untouched.

🌍 Your Environment

Software	Version(s)
Parcel	1.12.3
Node	11.1.0
npm	6.4.1
Operating System	MacOS

[mischnic]

The parcel documentation states that dependencies in node_modules get transpiled using preset-env

Where? Wasn't able to find that in https://parceljs.org/javascript.html.
This was initially done because running babel over node_modules would be quite slow.

Actually a duplicate of #1655