To get back to the main point - I am pretty convinced this was for 'vortex purposes'.
We use this quite regularly at my airfield. By asking someone to backtrack for a full length departure, you can often get an outbound airborne ahead of an inbound confortably rather than sweating on having to wait for 3 minutes. If you say 'NO' then then you will probably have to spend another 3-4 minutes at the holding point burning precious fuel.
I cannot quite understand why any pilot would refuse such a requst -the phrase ' there is nothing so useless as runway behind you' comes to mind!