I followed all the code to the end of the first part of establishing the theme and my AppBar Title text is left aligned. I added the centerTitle: true. to the AppBar Widget to fix this. see below.
home: Scaffold(
// TODO: Style the title
appBar: AppBar(
centerTitle: true,
title: Text(
'Fooderlich',
style: theme.textTheme.headline6,
),
),