Signals with invalid stock symbols

Looking at signalID = 51283948 from [LINKSYSTEM_46132063] this morning. The order is for TSX and according to Interactive Brokers there’s no such stock symbol listed on US exchanges. My trading process was unhappy and crashed.

Most likely the developer meant to enter TSX.GCE but entered only TSX. However, the question I’m really asking is, why was the TSX signal allowed?