I think these figures might be outliers - the 91 mpg seems incredible but I am sure you'd get more than 40 mpg at motorway speeds even allowing for the fact that high speed motorway work is not a hybrid's strong suit.
The worst I have had was about 49mpg on the A74(M) from Carlisle climbing to Beattock summit (IIRC they had to fit an extra railway locomotive for this climb in the 'old days'. ) Thats with only about 500 miles from new and the ACC set for 65 mph (where those around me may have had 70 mph showing on their speedometers.)
Maybe If I had set it for 80 mph it may have dropped to 40 mpg, but otherwise I dont know how these journalists manage get the figures they do. Perhaps they just look at the constant fuel consumption bar which with the engine running can drop below 35 mpg at times, but balanced up by the times you are not using any fuel at all. Or they measure it over a very short distance pedal to the metal.
I'd say at 65 mph on level motorway I got about 65 mpg ,sometimes dropping to low 60's. This may depend on tail wind or headwind. I got roughly 1 mpg less for every 1 mph over this speed and 1 mpg more for every mph under. But 80 mph + would come at a fuel cost.
But these are very rough estimates made over a short period. This is about the same as my Diesel yaris under similar conditions. A few small conventional petrol cars may equal, or slightly better it on the motorway. Its in town, and driven sensibly on rural roads where its fuel consumption is really impressive.