This has been fixed in v0.8.2
This was a multi-layered problem having to do with Babel config. So we can all say a huge Thank You to @peterp for the solution! 
If you’re interested, here’s the PR: Following tutorial and getting "ReferenceError: AboutPage is not defined" · Issue #630 · redwoodjs/redwood · GitHub
New Redwood installations are now using
v0.8.2.
Release Notes + How to Upgrade
There were a few other changes in this version, which you can read in the v0.8.2 Release Notes.
For existing projects, the easiest way to upgrade is to use the following command:
yarn rw upgrade