"It's because the 1954 definition is right."

So what were these songs before the 1954 definition? were they 'folk' songs when they were first written/composed,however long ago that may have been, or did they only become folk in 1954!!

'Folk' is merely the name we have given to a musical style and the 1954 definition is an attempt to define the heritage of that style. The definition (I believe) says that folk music is the 'product of a musical tradition that has been evolved through the process of oral transmission' I think the case that a new song which respects that tradition could be said to be a 'product' of that tradition and therefore be 'folk' would not be too difficult to argue!