Why the Delivery Preview API shows also publish content?

Question

As the title says why the delivery API shows also published content and not just unpublished content items. Here is how I initialize a delivery client for previewing content in ASP.net

public static readonly IDeliveryClient _client = 
        DeliveryClientBuilder
            .WithOptions(builder => builder
                .WithProjectId("ID-PROJECT")
                .UsePreviewApi("API-PREVIEW")    
                .Build())
            .Build();

Answer 1

Yes, this is expected behavior. As per docs :

The Delivery Preview API returns the latest versions of content items allowing your content producers to view content items before they publish them or preview changes made to already published content items.