What is `applewebdata` and how do I avoid it?
The support folks at Workflow replied in an email


  Those applewebdata:// URLs are likely local references to the image files that have been downloaded with Get Contents of URL that are now stored in the currently-running workflow. With Get Contents of Web Page, the input page converts the HTML to Rich Text and maintains the web links to each of the images.


The "solution" is to use the Get Contents of Web Page action, then.