After configuring a content filtering policy with the "bounce" action, bounce messages are delivered to the sender as expected but recipients still receive the original message.
Under the current design this is expected behavior. The "Send a bounce message" policy action sends a message which appears to be a normal email bounce message to the message envelope sender but takes no other action meaning that the message is still delivered.
The "Send a bounce message" policy action is commonly misinterpreted as "Bounce the message" often leading administrators to be confused when messages matching the content filtering policy continue to be delivered to end users. To reproduce the expected "Bounce the message" behavior, an additional "Delete the message" action would need to be added to the policy in question.