You’re not misunderstanding at all, and you’re exactly right:

https://arstechnica.com/gadgets/2023/06/duckduckgo-offers-its-privacy-centered-browser-in-a-windows-open-beta/

Like its Mac browser, DuckDuckGo (DDG) uses “the underlying operating system rendering API” rather than its own forked browser code. That’s “a Windows WebView2 call that utilizes the Blink rendering engine underneath,” according to DuckDuckGo’s blog post. Fittingly, the browser reports itself as Microsoft Edge at most header-scanning sites.