I do not agree. Many gospels were rejected because they were written far later than the earliest ones.  Regardless of the title of the book, who knows what else was in it that may have caused the Pope to reject it? Again, did he infallibly state that the Blessed Mother was NOT assumed into heaven? The Church does not work by innuendos when declaring something dogma or anethema. 

Of course my statement that you have no idea of a particular thing, in no way implies that I do know. We are speaking of something and someone from centuries ago- how can anyone now claim to know the mind of that person, unless we have written evidence of their intent?