fourteener
Omono
I think the screen is to stimulate finer root system through air pruning.
The wire mesh is not really about fast drainage as much as it it about getting the most air possible to the roots in this grow box. The more oxygen the roots get the healthier they will be, the more they will grow.
The wood on the bottom keeps the roots from breathing and taking in air from two sides instead of just one is really the point.