Furman - Korchnoi game question

So here's Furman - Korchnoi in 1954. I was going through my recently bought "Kasparov on My Great Predeccessors Part V" (Korchnoi and Karpov). This is the first game Kasparov went through.

I was wondering why 20...Qxe1+ wasn't played. It wasn't even mentioned by Kasparov in his annotations. From what I see, it forces mate.

The blue and white checkered board shows what I'm talking about. 20...Qxe1+ 21. Rxe1 Rd1 22. Rxd1 exd1=Q#.

He doesn't even mention it because instead of 22. Rxd1??, White has 22. f3, protecting the rook and creating an escape square for the king.

after 21...Rd1 white can also play 22. f3

... Qxe1; 21: Rxe1 Rd1; 22: f3

Ah', I knew there was a flaw in my logic somewhere. Thanks guys.