It all made pretty good sense. Norman told Pete not to tell Harry, so Spiderman probably told Bernard not to tell Harry. Thats why he kept it a secret for all this time. The night Norman died Peter probably told Bernard what happened and he believed him. If you saw a guy saving people's lives for months on the news I think you'd believe him when he said that Norman's own glider killed him. Bernard decided he needed to tell Harry the night Peter asked for Harry's help to defeat Venom and Sandman, so he broke his promise not to tell Harry and told him. Whether or not it all went down like that, its not a scene to really think about. His whole part in the trillogy was to make Harry realize his father was evil and that Harry needed to help Peter. He did that.