You're right that fzf doesn't replace find. Fzf is just an interactive, filtering tool. You can pipe anything into it. find is a common way of populating it with data.

I suspect the GP meant that fzf replaced the pattern 'find |xargs $binary' for small interactive use cases. It's much nicer to do '$binary <invoke fzf>'. I use fzf the same way with key bindings to select directories and files powered by find.