“(to avoid asymptomatic spreaders)”
No such thing. The state of the virus in which it can affect others arises only when an infected person is showing symptoms - already sickened by the infection. Can someone “appear” to not have symptoms (and even deny they do).
Yes. Anyone with any flu, flu-like symptoms should self-quarantine; order in their food and have delivery folk leave it at the door. But people should do that for flu anyway.
That's a fair point. Let me put it this way, as you did in the last sentence - you and I are not going to know the symptoms of someone we are in close proximity unless they are actively coughing or sneezing. They could have a fever and we would not know that, or if they have been coughing /sneezing previously and are not while we are around them.
Most viruses are contagious in the prodromal stage -— a certain number of days BEFORE symptoms are present. That’s why they spread so much -— we don’t know we/they have it, til it’s too late.