kicking directly into a force-7 wind
Yes, but you didn't say whether the wind was coming straight from behind the goal or, say, over by the corner flag. If he's kicking directly into the wind coming from over by the corner flag, clearly the ball has to travel further before crossing the goal line (albeit not between the posts).
That's Pythagoras' Theorem, that is. Though I suspect he probably expected it to be put to better use.