1 filters 'harmful' sites per the UT1 blacklists
2 is 1 + the new NSFW filter.
The new filter works pretty good in my assessment. It's not infallible, but it gives significantly cleaner results.
And if you do find queries it fails to sanitize, I'd love to hear about them.
So I can make sure I know what sites to stay away from, of course
The way the filter is implemented, it runs after the query has been executed. I'd have to run it at document processing time, code in a pseudo-keyword for the label, and then add that to the query.
It's doable, but I question whether the juice is worth the squeeze.