From what I remember you're right, the rest of the ingredients go in the shaker before step 4. I think there's been an automated standardisation to most of the recipes and some of them have got a bit muddled.
If you want to try an interesting variant of this… swap the rum for some Skrewball Peanut-butter Whiskey. I’d say it’s not as complex but if you like peanut butter on your banana or are looking to channel your inner Elvis - it’s not half bad.