Disagree - you have been cleared by ATC to push, ATC have NOT cleared you to release the parking brake, YOU do not release the park brake until ground have told you it is safe to do so, as they are the only ones who can see if it is safe to do so.
Standard call is
Cockpit crew to Ground crew “Confirm all doors checked closed and locked”.
Ground crew to Cockpit crew “All doors checked closed and locked”
Cockpit crew to Ground crew “cleared to pushback” (+ instructions on where/which way to face etc)
Ground crew to Cockpit crew “Pushback to face… (+ repeat the instruction of
where/which way to face). Release parking brake.”
Note: The request to the crew to release the park brake should only be made once “all doors closed and locked” statement has been made. See above.
Cockpit crew to Ground crew “All doors checked closed. Parking brake off. Blocks off
at …..”