"...putting common lines into functions, without careful thought about abstractions, is never a good idea..." (emphasis mine) I think this is the crucial part

"...putting common lines into functions, without careful thought about abstractions, is never a good idea..." (emphasis mine) I think this is the crucial part. DRY works fine and in fact arises naturally if the code is well factored to isolate areas of commonality - as the author points out though, this is very difficult to do and I think that's the core problem.