I think by your standard, many of the things commonly described as informal fallacies would not be such.
Also, I would not consider the informal fallacy to have arisen where there is disagreement about second order consequences. The fallacy arises where they are ignored or forgotten.
In other words to my mind the fallacy has not been committed if in the “birds on a wire“ example, those participating in the discussion have considered but disagree about what the birds will do consequent upon the first shot. The fallacy is committed where someone simply does not consider the fact that the situation will change upon the first shot.