It seems to be hit or miss. I've been told that American Airlines sometimes asks and Native Son sometimes asks. If you have something to show (example: a letter showing you home policy covers international illness) it will most likely satisfy the person checking. They are unlikely to stop and make sure it covers quarantine cost, medical repatriation, etc.

All that said, consider trying to find a policy that covers you for costs associated with quarantine (hotel, meals, flight change, etc). There are lots of people here right now that are wishing they had coverage. There are lots of positive travel test cases coming up and that cost is on the traveler to change their flights, find a place to stay, etc. We are full but getting requests for quarantine guests every day.