It is; I tried it last year - it is delicious! It reminded me of my childhood when sugar had only recently come off rationing so people had developed the habit of using as little of it as possible!
Perhaps that's why I am intolerant of the bucket-loads of sugar bakers use today (that, and T2 Diabetes).
It has a much more complex taste than the likes of the filling Mr Kipling use for their revolting mince pies.