I've tried testing this on the Edit Flow master development branch (https://github.com/Automattic/Edit-Flow/tree/master) in the following way:
1) Create a custom post type called 'books'
2) Create a post of custom post type 'books'
3) Write a few lines and preview it. Save it as a draft and preview it. Preview it from the Manage Books" screen
In all three cases I did not encounter a 404, so it appears to have been fixed. If you're able to download it and test it, please do. If not, v0.8 should be out pretty soon, looking to finish up a few tickets and then roll it out.