Definitely was true. Browsersers (at least FF) also used to add .com at the end. I think these days they all just send you to their ad-laden funding source instead if there is no TLD.(*)

https://www.thewindowsclub.com/browser-automatically-adds-ww...

(*) Apparently at least firefox still does the domain fixup instead of search if you type the http:// or https:// prefix so e.g. http://example/ will have you end up on http://www.example.com/