add a note that SuppressFlag is only used in the service it gets enabled

specification/trace/api.md

@@ -177,10 +177,11 @@ instance:
 The functionality listed above is necessary because API users SHOULD NOT have
 access to the [Context Key](../context/README.md#create-a-key) used by the Tracing API implementation.
 
-The `SuppressTracing` flag is for cases it may be useful to temporarily suppress
-tracing. For example, this may be used to prevent `Span` exports from being traced
-and exported, or by an instrumentation which wraps a lower-level package which
-may also be instrumented in order to prevent duplicate spans. 
+The `SuppressTracing` flag is for cases, within a single service, it may be
+useful to temporarily suppress tracing. For example, this may be used to prevent
+`Span` exports from being traced and exported, or by an instrumentation which
+wraps a lower-level package which may also be instrumented in order to prevent
+duplicate spans.
 
 If the language has support for implicitly propagated `Context` (see
 [here](../context/README.md#optional-global-operations)), the API SHOULD also provide