Landis makes a clear distinction here between the examination table and stretcher. In fact, he says they were in the process of removing JFK from the stretcher to place him on the table when he puts the bullet down. The explanation from Robenalt makes less sense if that is Landis recollection. He suggests that Landis wanted the bullet and body to be together for the autopsy. But according to Landis, JFK was no longer on the stretcher. Landis is also confused about the basic facts since he says the "magic" bullet was the one which hit JFK's head. He has also changed his story here to suggest doubt as to Oswald's guilt. The notion that Jackie dislodged the bullet is laughable.
Given how chaotic and traumatic that day was, it doesn't surprise me if he misremembers some details. I don't hold that against him.
He seems credible and while I give him some wiggle room on the details of what happened at Parkland, I don't think the detail of 'where' in the limo he found the bullet is easily forgotten or misremembered. I don't think a Secret Service agent, whose duty it was to protect the First lady, would mistake Governor Connolly's seat in the limo for Jackie and the President's.
The biggest problem I see with his recent account is that in the past, as early as 1983, he said he found a "bullet fragment" in the rear seat of the limo. Today, he's saying he found an intact bullet. There's a huge difference between a bullet fragment and a somewhat pristine bullet. The author of the book says Landis was misquoted in 1983 but I haven't seen Landis challenged directly on conflicting statements he's made in the past in recent interviews.