Indeed that's the exact frustration I have with them.

Whenever you feed an itinerary like ATH-FCO-DEL to the agent, they go to rates desk to find out the taxes. The rates desk can see this as a single ATH-DEL ticket and can calculate taxes accurately. However, their responsibilities end there and then. They aren't tasked with finding out the miles required with the same logic.

The agent then comes back to his/her own desk with the taxes in hand and proceeds to calculate the miles with the brain-washing they have received when they were inducted (i.e., point to point) and tells you the miles and taxes.
If you ask for the supervisors, they are only dumb agents who have been promoted by seniority, having zero additional ability and hence can't wrap their head around the single itinerary.

How I wish the rates desk were also tasked with calculating the miles required with the same logic they apply for taxes !