The Help topic is wrong in that regard. I cannot think of an instance when the join name would be an optional parameter. In fact the Help topic is pretty clear about the proper naming convention of the join name: http://resources.arcgis.com/en/help/main/10.1/index.html#//001700000066000000.Here is some of my own v10.1 Python code that uses the RemoveJoin tool:#Process: Populates the O_RB_DIST, O_RB_OID, and O_RB_WTY fields
oesfRipBuffFC = root + "\\layer_prep\\oesf_rip_buff.gdb\\oesf_rip_buff"
arcpy.MakeFeatureLayer_management(indxTileFC, indxTileFL, "FID_oesf_rip_buff > -1")
if int(arcpy.GetCount_management(indxTileFL).getOutput(0)) > 0:
arcpy.AddJoin_management(indxTileFL, "FID_oesf_rip_buff", oesfRipBuffFC, "OBJECTID", "KEEP_COMMON")
arcpy.CalculateField_management(indxTileFL, "O_RB_OID", "[oesf_rip_buff.LDO_OID]", "VB")
arcpy.CalculateField_management(indxTileFL, "O_RB_DIST", "[oesf_rip_buff.DISTANCE]", "VB")
arcpy.CalculateField_management(indxTileFL, "O_RB_WTY", "[oesf_rip_buff.SL_WTRTY_CD]", "VB")
arcpy.RemoveJoin_management(indxTileFL, "oesf_rip_buff")