Interesting that New Zealand and Australia were excluded from the study. Both had hard lockdowns and both eliminated the virus and are largely back to normal life. Makes me suspect the data was cherry picked to fit a desired outcome.
Being an island somewhat helps, but it's not like other countries don't have borders that they can protect. Bureaucracy is pretty low in NZ so we've been able to throw together solutions of screening, etc within matter of a week. Impacted workers got wage subsidy within like 5 days of lockdown started. Heck even Apple took something like 10x longer to release their contact tracing API...
Victoria had VERY had lockdown for months. Borders were shut to most states for months as well.
Aukland also had a hard lockdown for a few weeks.
However, there weren't country wide lockdowns, and they didn't last as long as they have in many other places.
At the same time. Speaking to family in the US, it seems the idea of "lockdown" is open to quite a bit of interpretation. My sister was complaining about the lockdown in California, and in the next sentence was telling me how excited she was to go skiing in a few weeks.....how do you go skiing in Colorado during a lockdown in California?
I don't think your characterisation of the NSW lockdown is entirely accurate, either. We were forbidden from leaving the home except for exercise in the local area within household groups, essential shopping and essential work. Schools were closed except to the children of essential workers, most offices shut down or reduced their capacity, cafes, restaurants, pubs and many other businesses were closed. It was a lockdown.
Restricting the rate at which it can spread through the community coupled with active and aggressive contact tracing certainly seems like it played a significant role. I'd be looking cockeyed at any study that chooses not to include the Australian and NZ datasets without a very robust case about why it's necessary.