AWS SESv2: Using contact attributes for template data

I have a contact list, with each contact having the "Name" attribute, such as:

{
    "ContactListName": "myusers",
    "EmailAddress": "john@gmail.com",
    "UnsubscribeAll": false,
    "TopicPreferences": [
        {
            "TopicName": "Announcements",
            "SubscriptionStatus": "OPT_IN"
        }
    ],
    "AttributesData": "{\"Name\": \"John\"}"
}

I would like send an email to all customers interested in a particular topic. The email is based on a template that begins with "Dear {{Name}}". I want {{Name}} to be replaced with the name from the AttributesData of each contact.

I can obtain the list of contacts interested in the topic using list_contacts. However, the response does not contain the AttributeData and so I have to send the email like this:

response = ses_client.send_bulk_email(
    FromEmailAddress='no-reply@mysite.xyz',
    ReplyToAddresses=[
        'feedback@mysite.xyz',
    ],
    DefaultContent={
        'Template': {
            'TemplateName': 'mytemplate',
            'TemplateData': '{"Name":"Unknown"}'
        }
    },
    BulkEmailEntries=[
        {
            'Destination': {
                'ToAddresses': [
                    'john@gmail.com',
                ],
            },
            'ReplacementEmailContent': {
                'ReplacementTemplate': {
                    'ReplacementTemplateData': '{"Name":"John"}'
                }
            }
        },
    ],
)

If I skip the ReplacementEmailContent key, {{Name}} in the template is substituted for Unknown. How do I get it to use the contact's attribute data? (Note that calling get_contact for each contact would take too long when sending bulk email to many users)

P.S. The question in SO