Full ACK - that would fix A LOT of issues, reminders being only one of them. There's also an issue with what happens when you tap on a reminder (iOS): Joplin opens, but you have to find the specific note for yourself. To guide you there, an additional pop-up is shown (vanishing quite fast, unfortunately). This pop-up is an improvement that's come with one of the latest updates, I think.
I'm a great fan of Joplin (on all platforms), but this must be the only app on the App Store that has no background sync and handles reminders/notification the way it does... 