Presumably the point here is marketing. So the question really is, Will the mention of this particular credential help to sell this book?
Some credentials would be a pretty obvious plus. If you've written a book about how to design automobiles, mentioning that you've spent 20 years as an automotive engineer for a major car company would surely be a helpful credential.
Mentioning that you have a degree in French poetry would sound pretty irrelevant. If you give a bunch of credentials that are all irrelevant, that would signal to me as a reader that you have no relevant qualifications, or you would have brought them up. In such a case, better to say nothing. Like, okay, this has nothing to do with a book, but I got a campaign flyer from someone running for office once that had a panel with his qualifications, and they all sounded trivial and irrelevant to me. Like -- seriously, this was one of the things he listed -- "Had perfect attendance in high school". Listing such things led me to believe that he probably wasn't qualified for the job.
Credentials mentioned might signal the reader what kind of book this is. Like if you've written a book about automobile design and you list as your primary credential that you've spent 20 years as an environmental activist, I think readers would expect that your book is going to be about the environmental impact of design decisions.
In some cases a credential could be taken by likely readers as a negative. A book on vegetarian cooking that lists as the author's main credential that he is chairman of the National Beef Producers' Association would likely lead vegetarians to question if this is a book they are interested in.
You may be able to tie a seemingly-irrelevant credential to the subject. Like, my first book was about database design, and my second book was about the Bible. So in the about-the-author stuff I wrote that I was a software engineer and that I brought this technical and analytic viewpoint to my Bible commentary. Whether that worked or not I can't really say. I'm sure that the principle works if done well. It can not only let you use the credentials that you've got, but if done right can give the reader the impression that you are bringing a fresh or special perspective to the subject.