This question come at a new customer recently. It’s been a known issue in AX2012 and it’s something you can work around but causes confusion when you first come across it when configuring routes. In a multi-step route you might go through multiple steps maybe some assembly first, maybe some welding next, then third step is some more assembly. So while you might call the operation assembly the resources might be different. But if you try to configure a route in AX with the same operation name and different resource assignment then you will notice that if you configure the first one and assign the resource when you configure or change the second step it will change the resource on the other steps that have the same operation name. You can work around this by just making sure that you use different operation names where you need different resources in the same route.
Here is a quick overview.
AX2012 R3 CU11