There are always exceptions to these generalities. Impact critics will usually find them. They also cite all sorts of anecdotal citation behavior which do not represent average behavior. The same can be said about alleged citation errors, most of which are really variants of one kind or another or do not affect impact since only variants in cited journal abbreviations matter in calculating impact. These are all unified prior to issuing the JCR each year. And a huge number of author errors or variants are corrected by the ISI system but unseen to the user.