I wonder if any more information is likely to be released by the authorities, especially regarding anything recovered from their cell phones, or any other findings from the autopsies.
Nguyen's family was told that "Rachel may have been in distress; her T-shirt had been wrapped around her head like a bandage."
One friend dismissed that Orbeso brought a gun with intent to murder, stating, "That is not the kind of person Joseph is... I think he brought a gun out there to protect Rachel. I think they got lost and were suffering in 100-degree heat." This agrees with Orbeso's father describing him as "a protector", as well as his occupation as a security guard.
Statements from friends and family of someone accused of murder should obviously be taken with a grain of salt, but as of yet, no one has come out to say that Orbeso displayed any psychopathic or sociopathic tendencies. And I think the act of luring a friend out in the middle of the desert to murder her would be pretty sociopathic. If he wanted someplace private, why not head down Geology Tour Road? Sure beats hiking in 100 degree heat.
Regarding their final resting place, Otherhand's scouting trip has shown that it would make little sense for them to abruptly head East, when if they followed the main wash, they would have reached town. But there is a possibility they climbed out of the wash in an attempt to get a call out. Then proceeded into the canyon where they were found.
The purple line is a route that follows the washes, and would go over the 40' waterfall where town is visible.
The dashed red line is a possible CC route. Red lines are existing trails.

Perhaps they hiked to the point where some left-behind snacks were found, then back-tracked, and hiked up a gently sloped wall of the canyon. Failing to get a call out, they proceeded North again, and entered the canyon where they were found. It doesn't seem like they would have been able to see houses at any point, except for possibly on the CC route, at which point they reacted normally by heading toward it.