A while ago I exchanged emails with RYA headquarters and they confirmed that these requirements are guidelines, meaning this is the minimum recommended experience one should have, but in the end you will be assessed on your actual skills, and they believe that unless you have done what is recommended you are unlikely to pass.
In any case I myself consider sailed miles are the shortest distance from A to B. Meaning that same passage
done under great following winds or on a hard beat with double actual sailed mileage would count as same distance.
All that said, I would suppose that if such question is being asked you would qualify as actual sailed and not as rhumb line, in which case why not go for a little more sailing?
and back to the original question I believe they consider the 2,500mn as shortest rhumb line distance