Who is going to discover it in that time? Not the maintainers, they've already released it. Their window for scrutiny has passed.

There is some sense in giving the early adopters some time to raise the alarm and opting into late adoption, but isn't that better handled by defensive use of semantic versioning?

Consider the xzutils backdoor. It was introduced a month before it was discovered, and it was discovered by a user.

If that user had waited a few days, it would just have been discovered a few days later, during which time it may have been added to an even wider scope of downstream packages. That is, supposing they didn't apply reduced scrutiny due to their perception that it was safe due to the soak period.

Its not nothing, but its susceptible to creating a false sense of security.

The xz backdoor went undetected so long partly because the build scripts were already so hairy and baroque that no one noticed the extra obfuscations that ran code out of a binary blob in test data. None of which was even in the source repo, it was dropped into the package build scripts externally just before pushing them to the apt/rpm package repositories.

The maintainers did notice in both of the recent attacks, but it takes time to regain access to your compromised account to take the package down, contact npm, etc.

All recent attacks have also been noticed within hours of release by security companies that automatically scan all newly released packages published to npm.

So as far as I know all recent attacks would have been avoided by adding a short delay.