Can You Beat Legends Arceus with ONE Rowlet?

*This was before version 1.1 was available, Massive Mass Outbreaks didn't exist at the time of recording*
(This was also my first playthrough of the game btw, so I didn't plan things out at all)
Can I beat the game with only one Rowlet? 🤔 I did this challenge on my main channel back when the game released, and thought I would post it here, seeing as this is a pokemon channel.
Main Channel - / @themrtrails
Main Twitch - / themrtrails