Short trips requiring the battery to warm up and then stopping shortly after will have poor efficiency.
Driving longer will give you enough time to “distribute” this warming up penalty, so the average efficiency will improve. This phenomenon is irrespective of city vs highway.
City driving is typically less efficient (ICE) because kinetic energy is lost as heat by the friction brakes every time you stop.
In EV, this loss is minimized by regen braking.
Highway driving loses efficiency due to exponentially more air resistance with the higher velocity that goes along with highway driving.
In ICE braking/acceleration losses overcome wind resistance losses making steady highway driving optimal.
In EV, thanks to regen, braking losses are not overcome wind losses. Making city driving possibly more efficient.
This is how I think about the issue. Simplified by ignoring other smaller factors like transmissions, weight, etc.