I think you're right that there could be better deflation rates technically and economically speaking. However, making it the same as Bitcoin makes it all easier to communicate and installs the powerful message of scarcity and future difficulty of obtaining more. I think that simple fact changes the mindset of people where the effort you make to earn tokens feels more important. So overall I think the decision to make it the same is good.
Curious to see how token distribution will look after a while. Imo proof of brain generally speaking works better when there are lots of people with a significant portion of the stake. Because that means there's a greater correlation between the amount of engagement and number of people voting on your post and the rewards. So you're more incentivised to form mroe relationships and get good reach on your posts.