I've no idea what you're talking about. Which, you know, makes two of us.
Firstly, Gr.B was introduced in 2017 with GT Sport, so no, it does not "always" mean that.
Additionally, the Citta di Aria and Costa di Amalfi events in GT4 were fully tarmac and called "rally", as was the Sierra Time Rally in GT6, so that's the historic perspective dismantled.
But ultimately it still misses the point made. "Rally" does not mean off-road racing, whether Gran Turismo has "always" used it to mean this or not (and it's not).