The one thing that I don't see mentioned is: are they actually protecting their vulnerable population while they do this, or are they just gambling at the risk of a 20% lethality rate?

Also, even if they do protect the vulnerable population, that only means they can stand a ~10x larger transmission rate. I don't think anybody knows how large it gets without some kind of action, but yeah, that would in theory make it possible to have milder actions.

That said, if they are indeed protect their population, I don't see how their plan differs from the rest of the world, that is trying to protect their vulnerable population too.

That doesn't seem like what they were proposing. From what I saw the idea was to flatten the curve at the point it is steepest, instead of trying to flatten it while it's still pretty flat, which just increases the time you need to keep countermeasures in place (because delaying only helps a little: it's very unlikely you can delay until a vaccine is developed, the main benefit of a few months delay is the NHS has less of its regular winter workload to deal with, which is higher than in summer).

Ouch. Good luck trying to get the timing right.

The earlier you start with countermeasures, the longer you can try them and see how they affect the spread rate. If you wait to impose them at the last minute, you will have to choose erring on too expensive measures or on letting your people die.

If you watch the press conference from a few days ago they say that their aim is the complete opposite.

The most charitable interpretation I can give it is that they're attempting the epidemiological equivalent of a suicide burn from rocketry.

A suicide burn is when you're trying to land on a body (say, the Moon) by letting your ship fall freely, thus accelerating with gravity, for as long as possible, and then at the last second, you fire up your engines at 100% output and decelerate until hitting the ground. When timed right, you'll end up touching the ground exactly as your vertical velocity = 0. It's the most fuel-efficient way of landing, but if you miscalculate that time just a little bit, you'll end up smeared all across the surface.

Suicide burn works in rocketry because you can calculate all the forces to extreme accuracy and precision. Nobody would even think of attempting that if the error bars on your altitude or velocity measurements were +/- 1000%, or if your engine output was unstable. Trying to pull the epidemiological equivalent - timing countermeasures to keep NHS at exactly 100% utilization - seems like an impossible task that's bound to end with a disaster.