Fuel blow back varies from car to car, and pump to pump, it seems.
There are some Shell and BP pumps I use where it never blows back and I can fill a full tank, like any normal car. But others getting the last third of a tank in takes for ever.

Try making sure the flap valve is aligned with the hinge at 12 o'clock.
Also, it is worth positioning the pump outlet spout at about 7 o'clock so it points directly to the filler hose.

Peter,
66, 2016 Porsche Boxster S
No longer driving Tarka, the 2014 Plus 8...