What matters is what the rule says.
At the start of its RtPh, a routing unit must designate its destination and must attempt to reach it during that RtPh...
When the rule talks about a routing unit designating its destination, what it of course means is that the player who controls that unit must make the designation. Similarly, when it says that the unit must attempt to reach its destination during that RtPh, it means that the player controlling it must ensure that it makes the attempt. Cardboard counters don't have the capacity to make that kind of decision.
The rout rules set out the parameters within which the player may choose the destination but, once that choice is made, it seems to me that he must comply with the very clear direction of A10.51. He must attempt to move the routing unit to its chosen destination. If, instead, he chooses a circuitous route (incurring interdiction into the bargain) with the clear intention of not moving the routing unit to that destination, I really don't see how that complies with what the rule says that he must do. It is doing the opposite.