I believe the multiple beeps are warning you that the car has not locked due to error or a fob is in the car/trunk. I can also get this beeping when I lean over the open trunk with a fob in my pocket.
I don’t think you can do away with the door close beep and still have walk away locking since it is the activation signal.
From the manual:
After the auto lock function has been activated, the auto lock operation stop beeper sounds for approximately two seconds in the following cases.
•The smart entry remote is put inside the vehicle through a window.
•You are located too close to the vehicle.
•The smart entry remote is put inside the trunk.
If the warning beeper sounds, check that you are carrying the smart entry remote. Then, open/close a door and confirm the auto lock activation beeper sounds once.