I think that depends a lot on what you mean by "functional". If "functional" means "everything is immutable" then I can guarantee that you'll learn a lot by programming that way. If you mean "first-class functions" then I cannot -- although you still might. You could probably program in Scheme (say) as if it were C with side effects all over the place, but that wouldn't teach you anything except a different syntax. OTOH, coding something non-trivial in Haskell would teach you a lot -- even if you don't end up using/liking it.

(Aside: I was somewhat disappointed by the blogger calling out the "Wolfram Language" as something special or to be admired. It's a ridiculous ad-hoc hodgepodge of a language. I stress the word language.)