Why does the Risk API return int64 or null for Checkout ID?

I am using the Risk API, https://shopify.dev/api/admin-rest/2021-10/resources/order-risk#top to check if the order has been flagged as high risk but some of the calls are failing because the Checkout ID value is an int64 for some of the orders and null for some of the orders.

Is this a bug on Shopify’s side or is this the expected behavior ?