On iOS 13 and above, "Integrated Call History" is displayed.

Regardless of whether "Integrated Call History" is turned on or off, you can always answer incoming calls without unlocking the phone.
If "Integrated Call History" is turned off, SkyPhone call history will not remain in the iPhone's incoming and outgoing call history.
Note that even if "Integrated Call History" is turned on, SkyPhone call history will not remain in the iPhone's outgoing/incoming call history when "Allow Contacts Only" is turned on.