No, not in my eyes. Rappers sample OTHER artists music etc and never get called out, which is more shameful than using your own material. Nothing wrong with sampling your own stuff, as long as it's not simply repeating yourself WHOLESALE.
American soul has used the melody of Glastonbury, which was obviously an unfinished song and played only twice live (if I remember correctly). It has a SNIPPET of volcano in it. It's basically like when u2 released 'mercy' on the wide awake in Europe EP. It was their finished version of the bootleg of mercy version knocking around on youtube.
To me, American soul is the finished version of Glastonbury. Glastonbury was never released and only played live twice.
It sounds nothing like volcano except for a 15 second snippet taken from that song.