I had expected that by compiling Config.pm, the Exporter would inject an import() method

It doesn't.  When you use @ISA='Exporter', the method would be looked up via inheritance.  But you can alternatively directly import Exporter's import method into your package:

use Exporter 'import';
[download]

Also, you probably wanted to call import as a method, i.e. using the arrow notation:

  Project::Config->import(qw(foo bar));
[download]