...but I couldn't really tell for sure.
Having no programming or coding skills to speak of, it's nice to learn that something like this couldn't have happened incidentally.
Maybe the amount of days should have been increased to like 7 or 8, but then again most ppl. wouldn't have used it, as a NPC combo can only bring it down by 5 days - it would then be cheaper timewise to travel twice 'around the corner', which wouldn't make much sense.
I can't remember how I came to learn this in the first place - I've known this trick for at least ten years - maybe I read about it before trying it out, or maybe I found it by roaming about in a game long ago.
I know I did roam about a lot in my earliest games (looking for out of reach chests and stuff), so maybe I did find it on my own, thinking everybody but me must've known this already - thus I never thought of sharing it :/
Once a party gets Water mastery it is not a very useful trick in the book. But I reckon that this would be super knowledge to a party of all Knights, Paladins, Clerics or any mix of the three, or even for a solo/duo of one of the three.
Anyhow it's always nice to know that it's useful knowledge to someone at this point 20 years after game release.