Why doesn’t the excess condensate filter down the toilet pan?

In a traditional toilet cistern it is common for the overflow to discharge down the toilet pan.

This is to draw any problems to the attention of the user to enable it to be rectified.

To avoid the possibility of a false alarm we discharge the excessive condensate to waste via a trapped connection, however should there be a problem with the mains inlet valve then this would discharge down the pan in the normal manner.