Yes, funerals are often a get-together with family you haven't seen for a while. It can be a good experience to catch up, and sure people share stories and laugh and 'celebrate life'... But I doubt anyone other than these two would call a funeral weekend 'amazing'. It's still a very sad occasion that deserves respect, no matter how much you might laugh and drink afterwards...
Oh, and about him not calling him stepdad and that being quite normal because his mum got together with him when Jonathan was already an adult.. sure, but it's not him not calling him that, it's him making sure that everyone knows that he was NOT (!!!!) his stepdad. He mentioned that a few times, really wanted to make sure the audience all knew that. That's what made it disgusting.