From the page: "Chrome doesn’t send a url to Google, it sends a url hash, so Google doesn’t learn the url from this exchange."

Surely Google has a database mapping URLs to hashes which means Google knows the URLs. The real question is whether Google logs the URL hash exchange which will allow it tie a user to a URL visit.

It's possible, but since this only occurs if the hash matches one of the sites on google's malware list, it shouldn't happen all that often.

the "send usage stats and crash reports to google" button was checked by default in my version.

Google distributes the installer with that option enabled if you check the box on their EULA that's shown before the download. You probably checked it out of habit without noticing.

That option is not enabled by default.