I was asked at imigration about 10 years ago when flying in on a one-way ticket.
I booked a open-jaw ticket with KL going AMS-HKG and a return with AF from HND-CDG and back home.
However, after staying in Hong Kong for a few days I flew on a one way ticket with DL with one of their fifth freedom flights HKG-NRT. (Going onwards to MSP I think.)
No questions during check-in or boarding in HKG, but I remember I had to show my return ticket with AF at imigration in NRT, so I am guessing they kept track somehow.