Being bored I did a little testing and this issue isn't restricted to this particular calendar app.
I downloaded the OP's app, set all required permissions and indeed it does not show in 'App notifications' in Settings.
I have no real use for calendar apps these days and I just use Fossify Calendar, solely as a simple calendar

and not for setting tasks, events, reminders etc, and on checking I found this is also a 'no show'.
I then downloaded DigiCal, and as the above another 'no show'.
Next I downloaded both Google Calendar and Samsung Calendar and guess what, they DID show up with the usual options etc.
Now whether this is a Samsung bug or a deliberate policy regarding certain phones and other third-party calendar apps I'm not going to speculate but that is what I found.
Samsung A36, Android 16 (One UI 8.0)