Next.js experimental `concurrentFeatures` and `rewrites` don't work

This is a minimal reproduction of a bug where using experimental.concurrentFeatures prevents rewrites from working.

This app was bootstrapped via yarn create next-app, the additional meaningful changes are:

Enable experimental features
Install latest React, ReactDOM, and Next packages
Add rewrites to next.config.js
Add bar.js page (which /foo should render instead)
Add _error.js page

Bug Reproduction:

yarn
yarn dev
or:
- yarn build
- yarn start
Visit localhost:3000

In Dev:

In dev (yarn dev), visiting localhost:3000/foo the page will hang and won't respond with any content.

Production:

In production, visiting localhost:3000/foo returns the _error.js page