The point is it's not as trivial as you say, and there's more to safety than pure input validation.
The author's point was that even people who think they're doing it right don't catch everything. If you think you do then I wish you the best of luck, but I also wouldn't want to work on safety-critical systems with you.
The author's point was that even people who think they're doing it right don't catch everything. If you think you do then I wish you the best of luck, but I also wouldn't want to work on safety-critical systems with you.