Sean has made a salient point.
My work, as a fine art photographer is often preliminary to the artist
handwork or as a final stage. In such cases both signatures are used on the final piece of art work.
To add perhaps a final quip in this sisypheran topic. The London Academy Schools of Art, including photography, take about seven years to get the graduates to a full state of competence in all processes.
A far as photography is concerned, such a graduate will be skilled to follow the various processes through to the end.
It may transpire that in his/her professional life it may not be feasible to complete all the work themselves. Nevertheless, they are in a position, skill wise, to make a judgement, to obtain the very best for the finished work.