Herd immunity isn't a strategy, it's an outcome
If a high proportion of a population, say 80%, is immune to, or vaccinated against, an infectious disease then the disease hopefully will wither away, because it has nowhere left to go. No host.
All epidemics, hopefully, will reach this stage at some point. The lockdown restrictions, light or heavy, attempt to manage when that will be. So all countries know they will reach that herd immunity stage anyway
I don't think there has been a massive difference in what most countries have done. The virus is new and not enough is known about yet.
ATM, unfortunately, it cannot be stopped dead in its tracks. Its a force of nature, like an erupting volcano or earthquake. But what can be done is limit the damage and the best way ATM seems to be to slow it down, flatten the curve, so that the health services are not overwhelmed all at once. Gradual lockdowns, then gradual lifting of lockdowns. Maybe waves of this strategy over the coming months . It's an experiment because it's new