(DOCSP-33865): Security clarifications to queryStats (#5132)

* (DOCSP-33865): Updates to queryStats

* style guide

* external review

Author: jeff-allen-mongo

source/reference/operator/aggregation/queryStats.txt

@@ -165,9 +165,18 @@ on the following data:
 
 - Database names
 
-``$queryStats`` **does not** apply the hash function to MQL keywords
-such as operator names (for example, ``$gte``), or parameter names (such
-as the ``partitionBy`` parameter in :pipeline:`$setWindowFields`).
+``$queryStats`` **does not** apply the HMAC transformation to the
+following data:
+
+- MQL keywords such as operator names (for example, ``$gte``).
+
+- Parameter names such as the ``partitionBy`` parameter in
+  :pipeline:`$setWindowFields`.
+
+- Field values. ``$queryStats`` normalizes field values in a query to
+  their data types (such as number or string) when the query is
+  recorded. ``$queryStats`` never stores field values that contain user
+  data.
 
 For an example of transformed output, see
 :ref:`queryStats-example-transformed`.
@@ -923,7 +932,8 @@ MongoDB Atlas Data Collection
 
 MongoDB Atlas periodically uses ``$queryStats`` to collect anonymized
 data about your queries, which helps improve MongoDB products. Your data
-may also be used to make feature suggestions based on usage.
+may also be used to make feature suggestions based on usage. MongoDB
+retains the data it collects with ``$queryStats`` for four years.
 
 When Atlas runs ``$queryStats`` on your deployment, it uses a unique
 HMAC key per Atlas organization to transform your data and avoid