Precisely.

It depends on what kind of actions they wish to do with the resulting scan/hack.

If they offer services to secure people/companies free or cheaply, then its a overall large positive.

If they give it to their equivalent NSA apparatus, that's a major bad.

Agree. Skillset and response will determine the success. Japan govt has a good precedence of centralized security scanning for country’s Internet, so hopefully it is a positive.

Vast majority of Internet users are not security savvy. Doing a baseline scan with appropriate remediation guidance will go a long way.

Given that they are announcing it instead of doing it secretly they seem to be starting with the right foot...

I'm pretty sure security researchers will set up honeypots and monitor what the government probes are doing.