I just did a frame-by-frame scan on the Room of the Harmonic Convergence for the Magellan episode, and it seems that the frontrunner never tried the "camera right/behind ladder" symbol combination that straddle where the potential half-pendant location is. It seems that he may have walked over them with 2:28/2:29 left on the temple run clock (before trying the door to the Swamp), but he did not apply the same stomping force as he did to the other symbol combinations. So based on that, the room may not have actually been a dead-end; it is possible that the door to the Heart Room simply did not get triggered. Notice that right after the frontrunner passes over that last symbol combination, Kirk says, "There he goes, he's got it." It seems fishy that Kirk would have said that if the room was meant to be a dead end... although that could just be another Fogg-Up...
Luckily, either way, the door from the Wall Climb to the Heart Room was unlocked, allowing this run to continue without too much chaos (unlike, let's say, the door mishap in War Fan of the 47 Ronin).
If this scenario is truly the case, then the frontrunner could have gone directly from the Harmonic Convergence to the Heart Room, getting taken out in the Heart Room. The second runner could then have followed that direct path from the Harmonic Convergence to the Heart Room and further (by following the path, she would have had to have entered the Harmonic Convergence, with the half pendant, and would have needed it later on). However, if the frontrunner had originally avoided the Harmonic Convergence, and instead gone straight to the Heart Room (which we know was unlocked from the Wall Climb), then he would have lost his pendant to the Heart Room temple guard and then would have been taken out by the Pirate's Cove temple guard. In following that path, the second runner would not have needed to enter the Harmonic Convergence, which would have then contained both the third temple guard and half pendant.