In the file: app\Http\Controllers\UserController.php
In the line: 581, find this section:
Remove the code: $running_order->orderstatus_id == 3 ||
Then the delivery guy details will only be shared with the customer when the Order Status ID becomes 4, i.e order is pickedup.
NOTE: make sure to backup the file before you edit anything.
P.S I have not edited and tested this myself.