It could be, and we may switch to unconditional checks just for safety. But the serialiser for traced message only passes on a deserialised TracedMessage if the system has a tracer, to also help protect:

https://github.com/akka/akka/blob/375fd6e44747d873211f38262f86bdb03dd45087/akka-remote/src/main/scala/akka/remote/serialization/TracedMessageSerializer.scala#L29-L32