I would say it's quite the opposite. Consider that the number of available points is more or less static regardless of number of players. In a 2-player game you have fewer players to spread those points around between compared to a 5-player game. This results in higher scores with 2 players, meaning the 10 point swing in having the extra longest caravan constitutes a smaller percentage of your total score than having the same extra 10 points in a 5 player game.
2-player games insure the value of gestures like walling off trees - points blocked are as good as points earned. this is not necessarily the case with more players, because your turn may end up having been spent shutting out a player that doesn't have a real chance to win while the one in contention is spending his moves 'for himself'.
if you have the lead in 3 colors and we both have 50 points, my overtaking a color would result in you having 40 and me having 60. with more players, if a source of points is stolen it might not necessarily be a struggle between the 1st and 2nd place players. if i take those same 10 points from the person in 3rd, it's 50 to 60 for a tighter finish. it's the guaranteed 20 point swing in a 2-player game on the 5th color that has caused me to observe this pattern.