The speed does increase from 50 to 70 at the north of this section and most notably, this section relies on ramps rather than traffic lights. If you prefer, you might consider tagging something like access_control for this instead of expressway. But personally I think the ramps constitute expressway-type design features for this section of road, which isn't necessarily the same kind of high-speed design as a motorway, just limited access and faster than most normal roads.