I don't think an airline would accept a passenger who has just tested positive for COVID. Nor would a hotel, unless it was one especially dedicated for COVID positive quarantine and run by public health people. This was done in China with positive cases. I doubt we'd want to convert the Diamond Head wing at HNL into a field hospital / quarantine center. The "instant testing" as part of the arrival flow raises these issues of what you do with the positive person in front of you, and what do you do with the other people who just got off the flight behind in line for testing or lingering in baggage claim. If you just 14-day quarantine or not based on the existence of a pre-departure test result paper, you then don't have to deal with these issues on the fly at the airport. And you could add the option Vienna also has of post-arrival testing once you're at your quarantine location and early release if you test negative. This does put more onus on the hotels to be enforcers though, which they're likely not super comfortable with.