I think you missed the part where it was 1983 (edit: actually even earlier, only the article is from 83).

I remember from "No Silver Bullet" (or was it "Mythical Man Month") how at one time it was a revolutionary idea to store documentation/comments along with the source code. It sounds crazy to ever have done it differently, but in earlier times, disk space was probably too scarce to do that. Likewise I suppose Mel's style was appropriate for the machines of his time.