WebDAV does not show up in my Files app either. What I’m showing is file browsing in the Pages app. Since the Pages app, and many others, use the Files interface, it is easy to forget what app you were/are in when viewing files.
Pages has built in WebDAV support, which is why it probably shows up there. When Pages first came out on iOS, WebDAV was pretty much the only way to use Pages with a cloud service (I used Box.com). It’s not needed these days.