The only people they are currently testing on arrival is those coming from The Philippines and possibly those who admit to having symptoms or have high temperatures when checked.
They lay out the rules for quarantine, but don’t ask you individually if your address is appropriate. The actual enforcement appears to be carried out by the county police/government, therefore the “closeness” by which you’re tracked also varies. You are officially allowed to stay with relatives as long as you have your own room/bathroom, keep 1m distance from them, wear a mask in common areas, and don’t eat together. Even essential (non-social) visits to your quarantine location are permitted.
When I arrived, the arrivals area where the CDC checks you filled out the online form was PACKED. No distance at all. If I was tested there, it would have been negative but exposure was absolutely possible.