You can do both. Iceland isolated their older population quite well.

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.

This requires a citation. It's intuitively far easier to quarantine 1% of the population than 90+%.

To protect 1%, you need to isolate them absolutely from everyone else who will be infected.

To protect 90%, it's sufficient if you reduce the rate of spread below 1, which means that it's sufficient to have a (realistically achievable) "quarantine" that reduces the number of contacts 3-4 times. It's possible to have much less contact with people, it's very limiting to have no contact at all.

There's a huge world of difference between the contact limitations required for a true quarantine (essentially, zero contact) and what "lockdown" has meant in most places, with most people continuing to work with other people just with much less contact.

It's not at all clear to me how much more limiting the isolation required for the 1% is than the current quarantine measures. I certainly doubt that it means "no contact at all". It's also not clear to me that a very strict isolation for the 1% is overall better than a moderately strict "quarantine" for the remainder (trolley problem). It's also not sustainable to maintain quarantine indefinitely, and the economic ramifications alone will compound (exponential--not linear--decay). At some point, "quarantine" becomes a net negative for the vulnerable 1%, never mind the remainder. Further, as so many things do, these economic impacts are and will continue to be the most severe among the most economically vulnerable. It's certainly sustainable for 1% of people to isolate indefinitely; it's not sustainable at all for the rest of society to quarantine indefinitely and that sustainability falls off earlier for the most marginalized communities than it does for the rest of us.

I mean isolation of vulnerable while letting infections elsewhere raise to saturation. No (non-micro state) country has gotten close to saturation/herd immunity yet.

I'm not sure if you're trying to refute my post or support it, but your comment certainly supports my point. No country has gotten close to saturation/herd immunity yet, and it would be economically ruinous (and not uniformly so) to maintain current quarantine measures until we get there.

I’m saying there is no one to learn from, no one did that strategy yet. The UK almost did.