Clip tests in the traditional sense were for dialing in your E6 materials for color balance and speed.
My first mentor I assisted for would buy his E6 by the lot number and then test at the beginning and have the CC he needed for that entire batch.
It was helpful for film speed and if any pushing/pulling was needed.

This was for 120 and he did alot of magazine work that was offset printed and the printer wanted you to have your color right so it was easier for them.