They are probably just testing the market out of Exeter so why position an empty aircraft down to Exeter when they can posssibly fill it with some passengers who are prepared to stop off at Exeter on both sectors , they have reduced the price of the holiday on the day of the flight going via Exeter or passengers can go non stop on another day
The same used to be done on the Jersey Tenerife service , passengers flew to Jersey from Bournemouth got off for the day while the aircraft picked up in Jersey to continue onto Tenerife then back in the evening to pick up the day trippers back to Bournemouth
Makes sense to make any sort of cash on an empty positioning sector