Any reason these wouldn't work for desktop use? The website seems very kiosk/signage oriented.

Electronic signage is one of the most popular use cases for PCs with such a small form factor. Those customers are willing to pay more of a premium than the typical home desktop user who simply wants a smaller footprint. But right now, AMD's focus with these chips is almost exclusively on getting them into laptops, not SFF PCs: https://www.youtube.com/watch?v=ACBDe1obhkM