Sure, but if you do both, isolating the elderly becomes easier because there is less prevelance and slip-ups are less likely to cause issues. It is a totally different strategy than what he was saying. The US stopped nursing home visits as partial form of isolation.

To fully isolate you would need workers to go through quarantine periods before entering on shifts. Many vulnerable live at home so you'd have to provide support to isolate their cohabitants as well or something else. Physician specialists that serve vulnerable and non-vulnerable populations without enough overlap to split duties with similar doctors between both populations would need to operate inside a bubble boy setup or something.

The vulnerable also include people with pre-diabetes, heart conditions, etc. that may not be diagnosed, though maybe you just treat them as those not to be isolated.