"Your wrist may vary"
It's easy to tell what they "recommend" because that's how they come mounted. Assuming of course that the straps actually COME WITH the watch, which is not always the case due to import regulations or CITES. They may come under separate cover, via a different source, or country, depending on where you are buying. So the factory doesn't always control what strap is on which watch or how it gets mounted.
Customer satisfaction is the ultimate choice of direction, I think. By swapping strap ends you normally move (rotate) the watch and buckle on the wrist, and that's what makes it comfortable for you or not. The loose end is sometimes an aesthetic choice, but what matters most is how the watch feels on the wrist and how it sits between the bones. (Conversely how uncomfortable the buckle feels against your desk)