I hear this, as well as "eliminates whole classes of run time errors" (as if Ruby and other such codebases are just ablaze everywhere on account of this...), but I wonder if people dabbled in this and think they have it all figured out, or if they've used a modern dynamic language like Clojure that has default immutability or been in a modern Ruby codebase that wasn't cowboy-coded.
They literally are, I think? Ruby is a notoriously unreliable language, in large part due to its dynamic type system... (also all of the unsafe idioms it promotes, a separate discussion)
For me, the idea of dynamically modifying code at runtime is like the first circle of hell. But I've programmed in enough languages to understand the appeal even if it doesn't fit with the way I like to work.
But I will take issue with blanket statements that static typing is more effort than dynamic typing with all things being equal. In my own personal experience, that is just not the case. But I wonder if many people have been so damaged by Java that anything seems better by comparison.