Yes this is literally just appending site: reddit.com to the query and redirecting to google. This page is a single HTML: https://github.com/goncharom/greggit

This was meant as a silly project! I caught myself adding site:reddit.com to a lot of google searches so I figured I’d just make a shortcut.

It would be interesting to know what exactly Greggit is doing. I'm no expert, but I think the owner of a website can prevent the traditional site: search from finding much of interest.