nobody compelled them to put inaccessable upgrades in the demo, or fake screenshots on the page. legit just don't do those things if the full game doesn't exist, it's not hard
You should see it as something you can get excited for when you buy the full game, so you already know there is more to do in the full game then in the demo and it sets a nice expectation for the full game. At least that is how I see it.
