Why Did the Triwizard Portkey Return Harry to the Outer Edge of the Maze?

[Harry] was looking up at the starry sky, and Albus Dumbledore was crouched over him. The dark shadows of a crowd of people pressed in around them, pushing nearer; Harry felt the ground beneath his head reverberating with their footsteps. He had come back to the edge of the maze. He could see the stands rising above him, the shapes of people moving in them, the stars above.

_{Goblet of Fire - page 583 - Bloomsbury - chapter 35, Veritaserum}

Harry and Cedric Diggory grabbed the Triwizard cup together and were transported from deep inside the maze to the cemetery in Little Hangleton where Voldemort was waiting. After Harry's confrontation with Voldemort, he takes the cup Portkey back to Hogwarts, but instead of taking him and Cedric back inside the maze, where the Portkey originated, it takes them outside the maze to the spectator stands.

My understanding of Portkeys is that they could take a person from point A to point B, and then bring them back from point B to point A. Is there any canon evidence suggesting that going from point A to point B, and then point B to point C is how a Portkey can normally operate? Why did the Triwizard Portkey return Harry to the outer edge of the maze instead of inside the maze?

Answer

As Dylan Yaga said in his answer to Why was the Goblet of Fire Portkey two-way? the most reasonable answer seems to be that the Portkey maintained the originally desired location akin to an onion.

The Portkey was presumably originally charmed to bring the winner to the beginning of the maze (so that they could celebrate their victory with the crowd). Before he put it at the center of the maze, Barty Crouch Jr. then charmed the Portkey to bring the winner to the graveyard.

This is supported by what we know from canon of Portkey's, (we only ever see them traveling in one direction, and not back to the same location). So it seems like the Portkey, which was originally designed to travel to the beginning of the maze, was itself turned into a Portkey designed to travel to the graveyard. After the first teleportation happened, the original Portkey remained.