As far as I know it's not a bug, it's by design - If any table/article is included in any active publication, then it cannot be truncated. From BOL "It is not permitted because replication cannot track the changes caused by the operation: transactional replication tracks changes through the transaction log; merge replication tracks changes through triggers on published tables."

For your reference:

http://msdn.microsoft.com/en-us/library/ms151740.aspx