I've towed both in factory setup and now our aftermarket setup, the bigger tyres, offroad tyres added roof platforms, bullbars etc they have some impact.
I'd be interested to see other people share thei towing economy data for everyone to review; but with your post of usage we also need to know what tyre you're running, size type, if you've also changed the alloy wheels (as that can matter, more on that in the future) added accessories such as roof platforms, bullbars and what you're towing as well - a photo goes along way if possible to see the setup!
Then we can see what type of fuel figures are really working with these new hybrid vehicles.