The answer is: No.
EPA has determined that returning a compressed gas cylinder to the supplier does not constitute disposal on the part of the customer. For most parts, the cylinder itself is the property of the supplier and the customer has no control over what the supplier does with the cylinder and its content once the supplier receives it. So the pressurized cylinder you are returning to the supplier is NOT a RCRA solid waste, according to EPA and therefore it cannot be a hazardous waste.
EPA’s RCRA online document RO14760 states that “returning the cylinder to the supplier does not make the customer a hazardous waste generator.”
Please note that you may still need to ship the pressurized cylinder as a DOT hazardous material.