White's idea in playing this way is probably that Black may be tempted to capture one stone on the edge; in which case White 6 captures in a ladder.
If Black is strong enough to fight hard here, Black 1 and 3 may make it difficult for White to live.
The staircase isn't often seen here in pro games, because extending with 1 is more like the proper play. Of course, White 1 is heavier, too. The original marked contact play is a technique that is occasionally appropriate.
Black connected solidly and succeeded in killing White. On the other hand White managed to break into Black's upper area by means of this sacrifice. Black did win the game.