Acol and modern Standard American use 2♣ as an artificial opening bid, showing a very strong hand, sufficient to force to game if the hand is unbalanced. In traditional Acol, you need either 23 HCP or five quick tricks in a powerful game-going hand. Usually responder bids 2♦ as a negative (or, by agreement, as a waiting bid).
With the first hand, you open 2♣ intending to rebid 2NT over the expected 2♦ response (this is the one sequence that allows you to stop short of game). With the second hand, you open 2♣ intending to rebid 2♠.
