"A classic example of this is Kate McNamara a superb Irish Concertina player that has been tutored by Mary McNamara (no relation). She has taken all that Mary has to teach her and added her own style to it."   
exactly, Alan,lets hope there is still room for many styles in irish music, otherwise the music will ossify.
My tutors are a song accompaniment tutor and an English Concertina tutor, the latter contains Scottish, English and Irish tunes, it make suggestions and discusses alternative ornamentation, at no point does it specify that there is only one way of playing ornaments, it is atutor to help people learn the English Concertina[nothing more nothing less].
Peter, Irish music will ossify and become monotonous if everyone ends up playing in the same style,
tutors have a responsibilty to try and show at least two different styles, or point pupils in the direction of recordings that show different styles.