I disagree with your third point. A player sampling the full game will now be able to refund a game if he/she doesn’t like it as a player playing a demo is less likely to buy the game after tryng it. From the article linked:

“Schell went on to assert that the best way to increase sales is to tease gamers with a trailer, and then to make sure there is absolutely no way the game can be tried out unless they buy a full version.”

So no, this isn’t exactly better for the developer if the developer is only concerned with making money (which not all are).

This argument is somewhat loaded though too. It’s like saying the average amount of legs that people in the human population has is less than 2 (because everyone has 2 legs while some has less which brings the average amount of legs of the entire population down). People who tried the demo may not have even shown up on statistics at all had there been no demo for the game.