While formatting ebooks for publication, many authors prefer to include an internal cover image. Indeed, this was the norm (and in fact, mandatory) for Kindle publishers up until recently; authors needed to provide an internal cover, as well as a second image for when the product is displayed on the Amazon site. This is no longer the case.
Now, only one product image is required. According to the KDP section when you are uploading the cover, Amazon uses this image in their search results, as well as your book's product display page, and now automatically embeds the image as your internal cover page. This means that inserting an internal cover is no longer required, and doing so will result in the cover appearing twice within your book.
Many thanks to Suzanne Parrott and M.A. Demers for the info!