Ha ha, just as I thought, absolute bullshit.
I have just checked the 1st US western I got in my hands from my collection. Ford's Wagonmaster. In the final shoot-out (1st scene I checked) there is even this ego shooter perspective I mentioned. you see Ben Johnson's arm and gun while he is shooting down a man in the backgound, who is also trying to shoot him. Very similar to Eastwood's first killing in FoD.
So that's a cinematic myth, which, despite the easily to verify fact that it's obviously wrong, is reproduced again and again.
Still, is there an old Hollywood film in which you see a double bed? That's probably a real Hays Code direction.
And tells you how censors think. Killing is ok, sex is immoral.