I know of some instances where a company's competitive edge is revealed in the process, not necessarily in the design. A previous employer of mine was in this category. Competitors could always buy our parts in service or aftermarket and tear down to reverse engineer them, but without knowing how it was processed they couldn't really duplicate the parts (they could take educated guesses and come pretty close). We did the same thing to their parts, we had an idea how they were made but weren't 100% sure. It was always fun getting a copy of one of their prints to quote (happened fairly regularly), but a copy of their
PFMEA would have been invaluable.
I think it's fair to ask your customer if you can submit a version of the PFMEA that has the confidential info deleted or changed to XXXXX.