I wouldn't put a lot of stock in either a speculative article or a random customer service representative determining whether amazon builds a new app. If you want it to appear take the 3 minutes to send amazon feedback to let them know what you want.
Here, I'll even write it for you:
Dear Amazon,
I've been a customer since {insert year that shows up on amazon.com home page when you're signed in}. I'm writing to let you know that as a Windows Phone user I'm extremely disappointed that you recently chose to discontinue support for the platform. Please consider creating a new Windows 10 UWP. This one application can be used on Windows 10 desktop, tablet, and phones and reach hundreds of millions of potential customers. Thanks.