Well I guess we see the detour differently.
To me, the detour involved constructing a raft and floating from Point A (the start of the float) to Point B (the end of the float). Along the way, teams had their choice of two tasks. Either deliver food to a village chief or hunt birds with a blowpipe. When teams finished their choice of tasks, they were given a "chit" to show they had completed one of the taks. At the end of the detour, they gave the "chit" to the man at the end of the float. Arrival at the end of the float with "chit"signified the end/completion of the detour and teams then received the next clue for the next part of the leg.
Dave and Connor may very well have been 4th to complete the deliver task, BUT they had already completed the float portion since they went all the way to the end. Then they carried their food delivery over land to complete their task. Leo/Jamal and Margie/Luke had to take time to repair their rafts, before completing the float portion. After the delivery, D/C got their "chit" and returned overland to get next clue. As we saw, they were the 1st team to finish the detour and get the next clue to the pit stop.