SQL deals with "sets", which are unordered, 
    and the user needs to specify the order by if 
    they need sorted output. I think this is an 
    excellent design.

Well-said, and I completely agree. However, I'm not sure that the author is complaining about SQL, so much as he is kvetching about some of the weird-looking things one needs to deal with while "working on a postgres-compatible query compiler."