The documentation indicates that all static and instances of a TopicClient are thread safe.
βAny public static (Shared in Visual Basic) members of this type are safe thread. Instance members also guarantee thread safety.
I read the quote that you included because it specifically includes TopicClient because it says "queue clients, topics, and subscriptions." I read this as QueueClient, TopicClient and SubscriptionClient.
, , , Gateway TopicClient MessageSender/Receivers.
, MessageSender MessageReceiver? , , , , , .