2 is not different for Option(al)/Maybe. 1 is simply not true in Kotlin: value?.let is both map and flatmap for value with nullable type. Which one depending on whether you return a nullable type inside the let (flatmap) or not (map).
It absolutely is true. The ?. operator is nominally different to map/flatMap. It does not extend to other monadic types and neither can you abstract with map/flatMap over nullable types. Not to mention more advanced type system features like higher kinded data that Kotlin can only dream of. Option can be mapped over types, ? can not. Option can be handled by sop-generic programming, ? requires a special case. Option is bijective, ? is not.
