I agree completely with what you say.
As far as I am aware, in my company, a phone call to MW does not let you depart a non-maint port with any defect that requires maintenance attention.
The only time you CAN depart a non-maint port is when you have a defect that does NOT require maint action.
The phone call to MW is required when any defect is recorded in the tech log. If that defect requires maint action then a phone call to MW does not let you depart the port.
However, there are situations where an airworthiness defect does not ground the aircraft, and the aircraft is still allowed to depart after a phone call. For example, an oxygen cylinder is used inbound to Kalgoorlie. That requires an entry in the tech log. The aircraft is down 1 oxy cylinder on departure. The crew are required to phone MW prior to departure and get approval to apply an MEL to depart. That can be done over the phone. The MEL allows flight with one oxy bottle used. Does anyone here have a problem with that? We are not talking about a thrust reverser inop.