How you know if its rape or not unless you go check?

The private property argument doesn't hold up that well because the car is on public property. Even in your own house if you on TV too loud and disturb your neighbours also its a problem. There's some civic mindedness that needs to be taken into consideration.

Personally, I DGAF if you wanna piap in a car. I see a car shaking up and down also I won't bother, I even accidentally came across a guy fingering his tudung GF in a car right outside a bank . I do understand why such laws/actions against the practice exists though. Otherwise everyone will just park car on the road side and piap... no need go hotel and you can see cars bopping up and down along the road

See my example about TV in your own house being too loud?

That's why "private property" argument doesn't hold up well. Doesn't really matter if its public/private. If you walk around naked in your home porch also will kena la. Recently some HK woman also kena in HK even though it was piaping at her own balcony

Like I said, personally I really DGAF, but its understandable why such laws exist cause people will abuse it otherwise.