We know that the family lived within 15 minutes of the trail and that JG searched Hites Cove on his phone app on Saturday. It seems to me that they arrived at the planned location, probably around 8 AM, and had no reason whatsoever to push themselves on this specific date. It's not like they couldn't return to Hites Cove on another day! I can't think of any reason why they would have hesitated to leave after 2 hours or less, unless they were somehow incapacitated. MOO
To go back out they would have to climb back up the way they came down. Maybe that made them think it wouldn’t make a difference whether they completed the loop or doubled back.
ETA: The fact that he searched Hites Cove on his phone that day indicated this wasn’t a simple, neighborhood hike. They weren’t familiar with the trail, IMO.