My friends who are used to dynamic type systems always say "How can you have so many problems? You must be inventing problems for yourself. I've never had a problem!"
Then I vocalise those questions you gave examples of, and they go, "Yeah, I guess... I just know my code so I don't need the type system to know that." Pah! Watch them write a million tests or suffer a million bugs.
It's funny how people using dynamic type systems seem to think they are superstar programmers who can handle having the system in their head at once, and people who are used to strong, static type systems are the ones to admit that they really... suck at programming and need all the assistance they can get to get it right.
Either there's a causality (bad programmers eventually find their way to static type systems and other tools they need) or one group has not yet realised that they are no better than anyone else.