You're also getting a massive boost to MGP, which is the main appeal of the event. It's when the most people do stuff in the saucer to get mounts/emotes/ect they've been putting off easier
The Make it Rain is basically a filler event, so it's no surprise it gives player little in the way of 'exclusive event items'.
Honestly I was expecting the minion to come from the Manderville relic weapon stuff, personally.