Most likely he was asked to reduce forward speed on downwind leg as much as possible for spacing reasons. The pitch up angle in slow flight with full flaps for a 747 is very impressive. I once experienced that flying into JFK and thought we were setting up for a go around except that the engines weren't going to full throttle and we kept sinking. In slow flight it does feel like it is flapping in the wind like any aircraft

A flare is something you do in ground effect just before landing.

What is even more impressive is in those rare instances when a commercial aircraft does a forward slip to lose altitude fast. Don't see many of those. There was one time when I could pretty much see the runway ahead looking through the FC window. I bet the pilot who decides to do that is a current glider pilot.