Yes, they introduced the concept in their paper. See this article for an in-depth guide to the topic: https://ciechanow.ski/alpha-compositing/

Great article! I'm going to have to take my time on that one.

But I guess I'm confused why @morio said "Just browsing the source I see Porter Duff blend modes. Really, in 2025?" because I'm not sure what they were expecting to be used in 2025.