He isn’t an average private citizen. He is a cut-out for the President. All Presidents use them.
There is probably some truth to this story. For example, the phone call could have been a heads up to the person who has frequently acted as the go between. Heads of State give other Heads of State notice and also sometimes tacit permission...as in we won’t object and go to war with you over it..etc.
How far it goes from there is something Schiff will seize on to find out.
The leader of Saudi Arabia doesn’t permission from us to arrest one of their own.
My guess is that when the President is looking for plausible deniability for very sensitive matter, the cutout doesn't' use a public line with other people listening in.