I think very little, if anything, has been proven for COVID-19.
The probability is that we already have all the answers to this virus, we just need time to work out which answers are the right answers.
In the meantime, we have a choice between high impact actions that slow the spread down and buy us time to find those right answers, or we go for a high risk strategy that may or may not work. I find the herd immunity approach an interesting one and it's certainly one that is worth considering, once we have developed enough treatments to negate the worst effects of this virus.
That said, I still believe a vaccine announcement is imminent (next few weeks) and that will feature heavily in any revised strategy.