I've read that before in ST's book and other places. It was well known she loved pineapple. I don't believe there was an intruder and doubt a stranger would know she liked pineapple anyway, and doubt she'd have gone with a stranger to eat it, liking it or not. If BR was the enticer I am sure she'd have thought it was a good idea, but his bribing her is something that may or may not have happened. If she liked pineapple that much, she probably wouldn't need to be bribed, especially by BR.
Patsy said she always had pineapple for JB in the house. I read an interview with Patsy long ago where she said she used to get fresh pineapple, but she bought it already cut up at the grocery store.
Who she was with when she ate it doesn't change much. She ate it- that is indisputable. I feel it had to be BR. And his refusal to talk to police about that night proves (to me anyway) that he was with her at some point after they got home and I feel he was with her as she ate that pineapple.