Clarify the enforcement of implemeting unique keys

Author: pellared

specification/common/README.md

@@ -80,7 +80,10 @@ Keys that differ in casing are treated as distinct keys.
 
 The representation of the map is language-dependent.
 
-The implementation MUST by default ensure that the exported maps contain only unique keys.
+The implementation MUST by default enforce that the exported maps contain only
+unique keys. The enforcement of uniqueness may be performed
+in a variety of ways as it best fits the limitations of the particular
+implementation (e.g. by removing duplicates).
 
 The implementation MAY have an option to allow exporting maps with duplicate keys
 (e.g. for better performance).
@@ -122,10 +125,10 @@ outside OpenTelemetry into OpenTelemetry attribute values.
 [Log Records](../logs/data-model.md),
 contain a collection of attributes.
 
-Implementation MUST by default ensure that the exported attribute collections
+Implementation MUST by default enforce that the exported attribute collections
 contain only unique keys. The enforcement of uniqueness may be performed
 in a variety of ways as it best fits the limitations of the particular
-implementation.
+implementation (e.g. by removing duplicates).
 
 Normally for the telemetry generated using OpenTelemetry SDKs the attribute
 key-value pairs are set via an API that either accepts a single key-value pair