This seems correct. Honestly, I don't think it's a problem with how you do it, but more the setup you've got.
Here are a few things I would try to fix it.
1) What happens when you assign concrete to all switches? If you still get Dirt, you are somehow not affecting the game, and therefore the SoundBanks you generate are not registered by the game, which would lead me to try...
1a) Did you make sure to put your lesson Wwise projects inside the Cube folder? Like this:
https://www.audiokinetic.com/courses/wwise101/?source=wwise101&id=installing_wwise_101_course_project_files
If so the SoundBank path in the Wwise project should be "..\..\..\cube\soundbanks\Mac" (since you are using mac right?)
Best way to make sure this works, is to delete them and regenerate to see if it then works.
1b) Do you have any other Wwise versions installed with Cube? If so, maybe you added the Wwise projects to the wrong Cube version?
2) In your capture log, search for "Material". If all of these are dirt, then yes something is wrong with your game. In that case, I'd normally ask you to report it as a bug in the launcher, but because I already checked it, I'd say we cannot replicate it and you should try reinstalling the game.