A (5,3), B (38,3) , C (3,2) and G (3,3,2) are used in the model.
A (5,3), B (38,3) and G (3,3,3) are used in the model. Note the difference between the w you specified and the G returned.
For a Tucker1 model with the first mode compressed A will be of size (5,3) and the core will be 38x3x3. Unfolded/Matricized, the core will be 114×3. For a Tucker1 model with the second compressed we will have B (38,3) and for the third mode compressed C (3,2).