Embankment/viaducts vs cuttings must explain much of the apparent difference.
Off the top of my head I can think of many GB mainline through stations which are below street level - Preston,
Which has two underpasses right next to one another (one with ramps to the platform and the other with lifts), although the city centre end is either ramp down to 3/4 from street level or via two over bridges from the Fishergate centre side.
Also approached from the south on bridges over the River Ribble
(Arguably it's both below ground level (city side) and at/above ground level (Christian Road) - presumably built by leveling off a section of the hill side - so a cutting on one side? Fishergate descends quiet a bit after it crosses the station.
Is Nottingham actually a below ground station as opposed to the entire station concourse being on a bridge over the station?
Most of the station is at ground level, but Station Street does rise up at the Carrington Street end meaning you enter the station at street level to go down steps to access platforms serving tracks at street level. Carrington Street also rises up passing the station front - much more noticeable coming in from the Meadows. The southern relief road (Queens Road/Drive?) also noticeably climbs up to cross over Carrington Street. I always wonder if this was the original lie of the land, or if the station building was built above the tracks with Carrington Street & Station Street ramped up to meet it?
Carrington Street is very much on a bridge nowadays and this appears to be well above ground level - The level of which immediately west of the station (i.e. at track level) suggests it was built above ground level.

(Photos shows Nottingham station taken from Wilford Street - surface carpark to the right is at track level, Carrington Street clearly a bridge (behind a gantry) and the bottom of the station building notably higher than the land in the foreground.
The buildings on the adjacent canal bridge are also built below ground level - the Carrington Street ground level being the first floor - so perhaps it was the canal that raised Carrington Street originally?
Rather handy by the other end of the station the canal is in a cutting and the railway passes over the canal on low bridges (there's at most 2.2m of headroom)

(Picture shows the canal bridge from the canal side, ground level clearly below street level)
The London Road end is on a bridge which noticeably rises over the tracks.