Yes, that is the one.
I know that this is not Hossein.
This actor (or more accurately stunt performer) appears in many small scenes in Spaghetti Westerns. Usually, these scenes are enitrely action-oriented and he is shot within a few seconds of making his entrance.
Even if I didn't recognize this actor's face from other films, it just simply isn't logical for Hossein to have done this small bit.
Scherp, look at it this way....would Hoseein travel to Spain to do just a few seconds of a film for someone he "might" have known because they were a friend of his friend, Leone? Also, this is largely a stunt sequence. I know the guy doesn't do much of a "stunt" as far as most viewers would be concerned. He just gets shot by Frank Wolff and falls straight back. But, believe it or not, that sort of fall is really dangerous to do, unless you are a trained stuntman (no matter how much they might have padded the ground). The scene only lasts a few seconds, but to make sure no one was injured doing the sequence, I am sure they spent a large amount of time creating it. You are dealing with a lot of factors in this very brief scene. Horses, firearms, make-up and costuming, the lighting, and so forth. I am sure it was a full-day, or a half-day worth of work. Hossein would not have just "been in the neighborhood" and volunteered to do this. It would have been something carefully planned and organized from the very beginning. Therefore, I think it is too much of a stretch of plausibility to think that Hossein would have traveled to Spain to take such a role--where there is even the slightest chance he might be hurt-- and that lasts only a few seconds without dialogue, for a director that he likely (at this point) did not even know.
Also, Hossein likes to talk about ALL of the things he has done in the movies..and he has never said anything about having appeared in GOD FORGIVES--I DON'T, to my knowledge.
So, even looking at it objectively, it really doesn't make sense that it would be Hossein.