At the end of the day, I am the one person who has to answer that question/is responsible for being GDPR compliant. I've spent hours doing research, figuring out what we need to do and implementing it -- and it's a hollow victory because even though I've said yes and have 100s of articles/white papers/opinions that back up the decisions I've made, the real answer is still "I don't know".
And I absolutely know I'm not alone in this. I got GDPR compliance dropped on my lap because I did security compliance -- if you contrast NIST 800-53/800-171 against GDPR you'll see why people are pissed off. One has clear guidelines with enough room for evolving best practices written by obviously competent/experienced professionals, the other is written as basically "we'll know it when we see it".