Seeing all those services hooked together gives me the willies. It sounds like a right PITA to debug, and chaining them together in serial for a single request multiplies the chance of an error even if each individual node is pretty stable. I guess it's okay for a demo though. They're probably not setting an example so much as trying to throw as many services together to show off the technique.
Ya the only way I could ever see this being maintainable is if it's declarative. It takes a tremendous amount of boilerplate and configuration to perform what comes down to a one liner in any functional language or a formula in any spreadsheet. I think I would be more interested in a transform that converts a series of goroutines to lambda functions or something.