It just sounds to me like Jonbenet grabbed some pineapple out of the bowl in the fridge some time before they headed off to the Whites' house.

Someone in the house the next day grabbed the bowl out of the fridge and set it out in case someone wanted something to eat. I doubt Patsy herself felt much like eatimg and really wasn't paying much attention to folks trying to be helpful in her kitchen.

Looks like Thomas didn't pay much attention to the fact that the pineapple fragments were already in the upper portion of the bowel and that the stomach contents contained only liquid. A huge waste of time trying to prove the pineapple was eaten just before Jonbenet was murdered, especially considering the autopsy report was available to him.