My position on where the family was and where they'd been.... IMO the assumption that they did a loop trip is backing good WS-ers into a box. If we give that up, there are many more possible scenarios. We also don't have a definitive statement from LE: with have an imagined map from the journalist.
So, you've got mom and dad, baby and dog. They park the car and get out. It's 85-90 degrees. They don't have a big plan for the day, but just want to stretch their legs and get out of the house. With COVID and all, they've been getting cabin fever. They've brought enough water to do just the little outing they have in mind, and maybe a little extra. Maybe there's rumors of a mine not far in or they have some other end point planned, maybe not.
So, they head down the dirt road to the gulch. Leisurely.... They're feeling great still when they reach the switchbacks. They go down a bit.
Then they realize the heat is really quite overwhelming, they anticipated there would be trees, and the baby is fussing. They know they didn't bring much water, and reckon they'd need more to continue. So, they turn around and head back to the car. Soon after (or 15 minutes or 30 minutes after, it really doesn't matter), the heat overcomes them.
A plan to hike the whole loop here is outlandish. It doesn't match with the couple's experience level, which was very solid and which would have given them many cautionary vibes. It doesn't match their parental responsibility, and we haven't heard from anyone that they were anything but super caring parents? I really can't see them doing the loop, let alone pushing through it to the end: it just doesn't fit. IMO the only way to signal that that's what they did is to examine their "carry in/carry out", so we'd know what scale of a trip they planned and what they'd used. If there's not much, IMO there's no way they planned to go far.