What is the regulation that prohibits removing an airworthy part and replacing with another airworthy part? If he didn’t feel comfortable with it or didn’t think it would make it to the next inspection interval, who are YOU to tell him otherwise? He very well could have prevented an incident. I’ve seen experienced guys change entire components when a simple seal change would have corrected the leak that was well within limits. If an A&P decides he should replace an airworthy part, his license (paper or plastic) gives him the authority to do so.