It looks strange, in Wwise Audio Lab Application footstep switch doesn't work correctly - it always triggers with 'default'. In the editor, it works well and triggered appropriate footstep sound for current surface (grass, concrete, wood, etc)
I faced this bug when setup own project. And then looked-up how it was set up in AudioLab.
After digging own project in wwise profiler log it looks like as the same problem - in the editor this switch works well, but in build - the switch forcibly set to 'Default'.
Okay, tried do not set the default switch (left the field empty), and in wwise profiler was appeared an error - the switch is not valid. Tried to set other default footstep switch (e.g. water), and always heard it on all surfaces.
Of course, I did some debug print string in BP - the material name was determined correctly. In wwise profiler, the Ak component for 'set switch' and 'post associated event' is the same and inhered by a local player. Footstep triggers from the animation like as in AudioLab.
Can u clarify for me, please, what's wrong with your setup in WwiseAudioLab? Because I looked upon it like as a reference implementation.