Phone app notifications

Hello,
In an attempt to hide incoming caller ID when screen is locked, I am playing with the notifications from the default and third-party phone apps.

Only to realize I don’t know really what a notification is for these apps.

So my question : when receiving a call, is the interface displayed ( caller ID, switches to accept or reject the call, etc.) a notification ?

If so, then the switch Settings->Apps->Phone->Notifications->Incoming calls->Lock screen->Show sensitive content only when unlocked or “Don’t show notifications at all” has no effect with the default app.

However, a similar setting for “Fossify phone app” has, for a short period of time (!) the effect I expect…

PS : the global toggle Settings->Notifications->Sensitive notifications is set to OFF.

Thanks !