Wallpapers are probably randomly selected in a small pool of available pictures. I used 3 different Windows laptops today: one was showing the Harry Potter ad and the two others a nice view of Bamberg.

Oof. Why does this seem worse than just showing everyone the ad? Maybe because people like me will go "not my experience" and brush off the complainers. Diabolical

Not sure either but I got the ad today. Previous wallpapers match what I see on bingwalls, but not the today's.

I think (based completely on anecdotal evidence) both the Windows desktop and lock screen pull their backgrounds from a different source than the Bing home page. I would often see a very different collection of image on my Windows machine (when I still had one) vs what I would get from the Bing Wallpaper GNOME extension I use on my Linux machines.