ModelBuilder.register does not generate a repack step with a pipeline session in V3 but does in V2

[mjost5v]

PySDK Version

• PySDK V2 (2.x)
• [ X] PySDK V3 (3.x)

Describe the bug
ModelBuilder.register does not generate a repack step with a pipeline session in V3 but does in V2

To reproduce
A clear, step-by-step set of instructions to reproduce the bug.
The provided code need to be complete and runnable, if additional data is needed, please include them in the issue.

model_builder = ModelBuilder(
        image_uri=image_uri,
        s3_model_data_url=data_url,
        source_code=SourceCode(
            entry_script="infer.py",
            source_dir=s3_script_archive,
        ),
        role_arn=role,
        sagemaker_session=pipeline_session,
        env_vars={"SAGEMAKER_DEFAULT_INVOCATIONS_ACCEPT": "application/json"},
    )
...
step_register = ModelStep(
    name="RegisterModel",
    step_args=model_builder.register(
        content_types=["application/jsonlines"],
        response_types=["application/json"],
        inference_instances=[inference_instance_type],
        transform_instances=[inference_instance_type],
        model_package_group_name=model_package_group_name,
        approval_status="Approved",
    )
)

Expected behavior
A clear and concise description of what you expected to happen.
In V2, the model was repacked with the code present. In V3, the model is not, leaving the model unable to be repacked

Screenshots or logs
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System information
A description of your system. Please provide:

• SageMaker Python SDK version: 2
• Framework name (eg. PyTorch) or algorithm (eg. KMeans): ScikitLearn
• Framework version: 1.4.2
• Python version: 3.11
• CPU or GPU: CPU
• Custom Docker image (Y/N): N

Additional context
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