There are some older files on boardgamegeek with rules for Haggis which include a line like:
Suggesting that the first player to go out gets an additional 5 points. This is in addition to the 5 points earned for betting "5", and 5 points for every card in the hand of the player holding the most cards. When did this rule appear, and disappear, from Haggis?“1st Winner” 5 pt. bonus for going out “1st”.