In below issue, is discussed whether the routing logic really works as it should:

When I look into the code, I find some strange logic in Plsqlap_Server_API.Find_Queue___. The function Get_Content_Only_Cond_Cnt doesn’t work as it should. It will never find anything due to incorrect first join. Below statement if from 24R1:

To me, correct statement would be as below. Then, routing rules without any conditions will be found. It will also mean that the other routing rules logic in total will work as expected
 

It means that you can setup any valid data and route it accordingly. Below setup on customer, which means that you can choose any of below choices at the time of sending the invoice:
 

Route in IFS Connect according to your setup on customer:
 

So, I would guess that this is a bug. Please let me know if I have erred in my assumptions.