IIRC, they tried that in Italy. It didn’t actually work because as a practical matter it wasn’t possible to isolate that many people.
Close...
Italy was an early hot spot. By the time they implemented the plan, COVID had gotten loose in their nursing homes and the disease induced pneumonia dammed near wiped out their old folks homes in Northern Italy.
If they had gotten a handle on what needed to be done 3 weeks earlier, the result might have been much better. Sweden didn’t do full lockdown either, but if you look at the gross statistical metrics of deaths per million, etc., there is not a lot of difference.
It seems everyone in the world has had about the same progress of this bug, no matter what form of restrictions or lack thereof was done.