Struggler, I would kick up a stink as it is very explicit at https://www.xara.com/uk/web-designer...#fitvid787204:
Responsive Web Design
This feature is in both Web Designer & Web Designer Premium

With Web Designer you can create multiple variants of a site - eg desktop, tablet, mobile - which are exported as a single HTML file, so that your site will dynamically change layout in response to the screen size of the viewer. What's more you can opt to scale the site to fit the browser width within variants, which ensures a better result for a wider variety of devices, and a smoother, more fluid transition within variants.

Example (The Auberge theme with desktop and mobile variants and 'scale to fit width' on)

Does your website pass the Google mobile-friendly test? If not, you need Web Designer!
Ask for a full refund but suggest a free upgrade would clear the air.

I had to download this to get it to play: https://www.xara.com/uploaded_files/...esponsive4.mp4

I am curious if XWD can handle a Scale to Fit Width design.
See if this scales in Preview: Xara - STFW - W1200 - Max1800.xar

Acorn