Because that’s an inaccurate statement. Or, rather, it isn’t wholly accurate. On the whole, you can expect someone who plays more, both games and ice time, to put up more points.
However, you would also expect the proportion of those points to be doled out differently. Players get fatigued. Playing more minutes means there are less favorable situations to take advantage of. There are a lot of variables here.
So yes, more ice time and more games should give you more points, but the efficiency at which you score those points will decrease.