Reminders app not showing in Location Services
I was trying to create reminders via Siri. I went to the Reminders app and created one there, I tapped onto the location and was again prompted that I needed to authorize the app to access my location. This time Reminders showed up!

So, I hope that if anyone else is having this issue they can solve it by attempting to create a reminder in the app itself, and not just through Siri.