For a member with an unsymmetric cross-section, the load plane runs through the center of gravity of the cross-section and not through the shear center.
Therefore, there should be torsion.
However, the results show: M-T = 0!
The loads are relative to the shear center in RSTAB.
An intentional torsion due to the section geometry (center of gravity not equal the shear center) is therefore not considered.
The RSTAB graphic with the system line (=centroidal axis) and the load applied to it can lead to a wrong conclusion.
Therefore, if you want to consider the torsion due to a loading which does not act in the shear center, an additional torsional moment (load x distance to shear center) is necessary.