Clarify that attribute processor does not drop signals (#5178)

* Clarify that attribute processor does not drop signals

* Use admonition type="note"

docs/sources/flow/reference/components/otelcol.processor.attributes.md

@@ -164,6 +164,12 @@ For example, adding a `span_names` filter could cause the component to error if
 
 The `exclude` block provides an option to exclude data from being fed into the [action] blocks based on the properties of a span, log, or metric records.
 
+{{% admonition type="note" %}}
+Signals excluded by the `exclude` block will still be propagated to downstream components as-is.
+If you would like to not propagate certain signals to downstream components, 
+consider a processor such as [otelcol.processor.tail_sampling](../otelcol.processor.tail_sampling/).
+{{% /admonition %}}
+
 {{< docs/shared lookup="flow/reference/components/match-properties-block.md" source="agent" version="<AGENT VERSION>" >}}
 
 One of the following is also required: