We need to establish what exactly counts as a shortcut. Let's get into it !

Hm, I'd say the definition of a shortcut would be to totally disrespected the road.
For exemple, the cut to go straight on racetrack instead of turning would be considered a shortcut.
The smoll cut for port at the start (that you can see on my speedrun please like and suBskcribe clik the nOtIFiCaTioN BeLl") would not be considered a shortcut.

Better said, a shortcut should be defined as:
"Cutting the track in such a way that you are not following the road intended by the developpers.

Exemple: On racetrack, there is a series of slalom near the end of a lap. Instead of going through the intended way the developpers want you to do, and do that slalom of the road, you go straight. That is a shortcut.
The small port shortcut when you start to go at the right of the containers instead of the left, is not a shortcut, but a corner cut."

simple, if all 4 wheels of the car come off the limits of the road or tarmac, it's a shortcut

+ this is easy to moderate
+ establishes skill-based corner-cutting with a partial amount of the car off the track

- doesn't allow minor corner cuts like RaceTrack turn 1 or the various hairpins on gunma, the hill etc