I get puzzled when I read "We prefer ....." when dealing with a grammar point.
In "Swan's Practical English Usage" I found this ...
A. Why are you crying? ---B. My brother HIT me. (Not HAS HIT).
Does this mean that "the present perfect is not O.K.?"
When Swan says that one construction is preferred to another, the meaning is not that the other construction is ungrammatical, but rather that it should be avoided.
Preference should be given to the preferred construction. He gives you the reason for this particular preference in the passage you have attached. Note how he says "usually":
". . . we usually prefer a past tense when we identify the person, thing, or circumstances responsible for a present situation." (Swan)