iCloud Reminders Not Background Syncing Between iOS and macOS

I sync my Reminders app via iCloud between iOS and macOS. On macOS, the reminder notifications are always outdated (compared to what they are on iOS) and don't sync unless I open the Reminders app for 3 - 5 minutes. Is this a bug or a feature? I thought I should be able to sync the Reminders app via background refresh without opening the app on macOS.