Problem with that theory is some of us are prepared to face 1.f4. I actually have 2 lines that I play against it, depending on mood and situation.
1...e5, the From's Gambit, against which I play 4...Nf6 or if White plays the King's Gambit, then 2...exd4 and 3...d5.
1...Nf6 which is fine for Black in reversed Classical Dutch lines, and if White tries to go reverse Leningrad, it ends up being a direct transposition to the Closed Sicilian, Spassky's Variation (the lines with 6.f4).
So looking for unprepared openings? Look again!
I wanted to list some moves that you can use with White to avoid the theoretical battle and just start playing Chess. In this video, I discuss about 1. f4, 1. Nc3 and 1. b4
After this, it is likely that both you and your opponent are in unknown territory as soon as move 2.
Sometimes you just want to get a decent position and play from there