Tweak default zero value doc wording

Author: JordonPhillips

docs/source/1.0/spec/aws/aws-core.rst

@@ -1113,11 +1113,11 @@ Trait selector
 Value type
     Annotation trait.
 
-When a member is marked with this trait, it SHOULD always be generated as
-optional even if the member also has the :ref:`required-trait` or
-:ref:`default-trait`. This allows documentation generators to indicate that a
-member is required, even if it is not reflected in the generated code. For
-example:
+When a member is marked with this trait, non-authoritative tooling like clients
+SHOULD treat the member as optional even if the member also has the
+:ref:`required-trait` or :ref:`default-trait`. This allows documentation
+generators to indicate that a member is required, even if it is not reflected
+in the generated code. For example:
 
 .. code-block:: smithy
 

docs/source/1.0/spec/core/model.rst

@@ -804,10 +804,8 @@ provide member accessors that always return non-null values.
   with their :ref:`zero values <default-values>`.
 - When the :ref:`required-trait` is present on a member, the corresponding
   accessor SHOULD always return a non-null value.
-- Smithy implementations in languages like TypeScript that do not provide a kind
-  of constructor or builder to create structures may not be able to set default
-  values, precluding them from being able to treat required and default
-  members as non-null.
+- An explicitly provided default zero value and a member that defaults to the
+  zero value are indistinguishable.
 - Because the :ref:`required-trait` can be backward-compatibly removed from
   members of structures marked with the :ref:`input-trait` (that is, the input
   of an operation), code generators MUST generate code that does not break if

docs/source/1.0/spec/core/type-refinement-traits.rst

@@ -24,7 +24,8 @@ Summary
 Trait selector
     ``structure > member :not(> :test(union, structure > :test([trait|required])))``
 
-    A member of a structure that does not target a union or structure.
+    A member of a structure that does not target a union or a structure with
+    required members.
 Value type
     Annotation trait.
 
@@ -48,9 +49,8 @@ Default zero values
 
 The following table describes the default zero value of each kind of shape.
 Programming languages and code generators that cannot initialize structure
-members with the following default values SHOULD continue to represent those
-members as nullable as this is semantically equivalent to the default zero
-value.
+members with the following default values SHOULD represent those members as
+nullable as this is semantically equivalent to the default zero value.
 
 .. list-table::
     :header-rows: 1
@@ -67,10 +67,10 @@ value.
       - Numeric zero.
     * - string
       - empty string
-      - Strings with the enum trait also have the same default value.
+      - Strings with the :ref:`enum-trait` also have an empty string zero value.
     * - blob
       - empty blob
-      - This includes blob shapes marked with the :ref:streaming-trait`.
+      - This includes blob shapes marked with the :ref:`streaming-trait`.
     * - timestamp
       - Unix epoch
       - Zero seconds since the epoch (for example, ``0`` or