Answer:
In principle, the modified cross-section properties are not transferred into add-on modules, such as RF‑/STEEL or RF‑/STEEL EC3. They are only used for the calculation of internal forces.
In the add-on modules, stresses are calculated using the real cross-section dimensions, which cannot be modified. This would be difficult to implement, as many design checks require the element width or height and due to the modification, it is not known exactly which parameter has been reduced. This is important for c/t-designs in RF‑/STEEL EC3, for example.