I won't speak for the podcast nor their writers on their credibility nor access of credible information. As this entire forum is "allegedly for educational purposes only", I do understand being hesitant about past garage sales but I think it is worth looking through this lens as this seems to haven taken place in a very specific manner. I found a few other sources that also allege that the Barraza's often did an annual sale of items (like spring cleaning) in their other previous properties.
Also important to mention, they have had several other houses & properties before they settled into their current home thus this may have been a "new thing" for others to see of her OR unknowingly their new neighbor reports that they haven't seen a garage sale by them before. Even if her previous neighbors (from other properties/residences), may be able to give a better understanding as who the perp may be & why this specific time/date was chosen.
IMO the timeline is very odd including my own perception of the suspects behavior. Unresolved also did an article on this case in which I found similar findings in the Criminology podcast. Unresolved site lists resources through: Crimestopper Houston division press conference, 911 recording statements, detective/investigator interviews, and Harris County Sheriff's Office.
"On the morning of Friday, January 25th, 2019 a woman was setting up a garage sale in the driveway of her home. This was an annual event that she held every year, in her sleepy neighborhood in southeastern Texas."
Speaking to the press about this update, Detective Wallace Wyatt - the newest detective assigned to the case - stated:
"You see Liz in the video notice the gun and she jumps, it scares her. I think Liz then, may have known that person.
"Liz reacts, scared. There is some muffled something going on there. We're not sure what was said by the suspect, and then, shoots her three times. She falls to the ground. This horrible, calculated, premeditated and pitiless murderer steps over her and shoots her again in the head.
"About two minutes later, the suspect drives back to look at their work, seeing what they've done, to make sure Liz is dead."
Elizabeth Barraza — Unresolved
(HIGHLY SUGGEST LOOKING INTO HER SOURCES AS SOME I HAVE NOT BEEN ABLE TO COMB THROUGH --> BUT MAY BRING NEW SOURCES/ARTICLES TO INVESTIGATE IN ALIGNMENT WITH WHAT WE HAVE BEEN ABLE TO FIND & PUT ON THIS THREAD)