It's pretty handy to only have to be vigilant at the boundary layer. With the untyped approach, all consumers of the deserialized map have to guard against data

It's pretty handy to only have to be vigilant at the boundary layer. With the untyped approach, all consumers of the deserialized map have to guard against data which doesn't conform to expectations. With the typed approach, all subsequent functions only have to work with data conforming to the specification as laid out by types.