What this is (and isn't): this holds the actual track fixed — for every wind angle/speed combination actually sailed, it asks "what if this exact segment had been sailed at the polar's speed instead of the boat's," then sums up. It does not model routing changes a genuinely faster or slower boat would have made — reaching a layline sooner, avoiding a header, riding a shift longer, timing a current gate differently. Different boatspeed in reality would very likely have meant a different route, and therefore different wind angles and conditions than what got sailed here. Treat this as "how the actual angles/speeds compared to target," not a true alternate-history finish time.