The average time to unlock now is faster because The Wonderful End of the World is going really quickly. Killing floor has been averaging more players (Over double the amount at all times) of TWEOTW, and look how far it is behind every other game.
It'll be fast until the easy games are gone, and then grind to a halt as soon as the last 4 or 5 ones like Killing floor, The ball and Amnesia are left.