It's not sarcasm: the conventional wisdom was that an SF novel could not also be a satisfying mystery/detective novel, because the readers could not guess that Aldebaranians can see in ultraviolet, or any other authorial invention.
Asimov's insight was that it was up to the author to play rigorously fairly: every fact of consequence needed to be revealed naturally.
And that's what I love about the robot stories. He sets up the law of robotics, just like Agatha Christie and friends set up the detective fiction commandments, and then Asimov sets about finding all the loop holes in the laws of robotics. Every story is one loop-hole.
Asimov's insight was that it was up to the author to play rigorously fairly: every fact of consequence needed to be revealed naturally.