I think it comes down to what is most probable. If the Nissan Frontier Pro-4X was spotted at 2 am (or according to Arrin Stoner's video 12:30am) coming down a certain street at that time police are going to check out every house on that street to see about vehicle registration addresses for that vehicle. My guess is police did exactly this and got vehicle registrations for Nissan Frontier Pro-4X trucks for the entire subdivision.
Whether it is the vehicle itself or the license plate or the murderer, one question I would like to ask Elizabeth Barraza's husband would be, "Did she usually go out a little after 6 am to go to Starbucks and return around 6:15 am each day? Was it just that day or was going to Starbucks in the morning at least a 2-3 day a week occurence?" The reason is at the end of Arrin Stoner's video, he has bonus footage. The bonus footage is of Elizabeth Barraza getting into her car and warming it up for about a minute, then leaving to go to Starbucks. Then she returns, parking the car on the street, and going inside the house.
Why did the killer not commit the crime then? It was still dark outside. Whether when she left of when she returned, if the killer had shot her then, they could have gotten in their vehicle and been out of there before Sergio even came outside. Plus, identification would have been very difficult, especially of the killer.
Maybe Sergio might say she went to Starbucks often, but I would have gotten surveillance tapes from inside Starbucks and the drive-thru for 6-7am to see how many times during that week leading up to her murder, she went to Starbucks at approximately the same time as the morning of her murder. My opinion is that the killer was waiting for her to leave for work and expected that to happen at around 6:30 to 7 am. The killer may never have seen her leave to go to Starbucks that morning.