This doesn't make sense. Assuming it's worn on the left wrist, and the crown is on the right of the watch face, then the crown is _always_ facing down (when hands are down) - no matter if you're wearing it on the inside or outside of the wrist. Am I misunderstanding something?
This part seems like an unfinished thought. I thought they meant to say that being on the inside of the arm would mean that the crown is less exposed towards splashes, debris, and whatnot from the outside.
The crown facing the hand is a carryover from traditional watches where the user would need to regularly wind or adjust the watch's time. It doesn't really have any benefit now, and just needlessly exposes the crown to shock damage and irritates the back of the hand if the watch falls towards the wrist.
Seiko diving watches and some others move the crown to the 4 o-clock position where it's slightly less exposed:
