With a bus/truck they remove the bodies (usually). These ships went down with people in them and are graves. There is a difference.

It would be like you being buried in a coffin in a stone church and then one day someone decides they want the stones and they take the whole church ... including you :) As a relative i would be pretty pissed about that too.

If they were correctly identifying bodies and returning them to their families for proper burial etc... then it might be ok to reuse the steel.