It looks to be similar to Nvidia Canvas - there's a good demo of that online.

Basically the user paints where they want a feature to be using a colour. The AI replaces the colour with a feature and makes sure that any features touching eachother blend together beautifully to create a believable human face.

Yeah, it's Nvidia Canvas for faces, except not trying to sell you RTXs. Instead we're trying (when we load balance) to offer a realtime service through the browser. I have some more background in a comment here https://www.producthunt.com/posts/face-maker-ai