TL;DR: there's value in showing examples outside the nextjs ecosystem.
https://github.com/witoszekdev/dummy-payment-server has a lot of value in that it's simple to read and understand, unlike the nextjs dummy with all it's redundant abstractions and requirements of specific knowledge of react / nextjs.
Since it's written in a few typsecript files, it's easier to learn from it. I used it as reference for my own apps instead of the official saleor ones for this reason.