As i mentioned above, ours were certified as Cat C, no matter if we used flaps 40, which went up to over 140kts, or flaps 30 which was nearly always faster. For circling we used the larger area of Cat D though.
I don't know what you mean in this context by "coding", but the FMC displayed threshold speed was variable and adjusted according to chosen flap setting and weight plus inserted wind correction (minimum 5kts).