Was asbestos used within wallboard itself, or just in the joint compound?

I'm pulling down a few walls in my 1984 house. I had a company come in to do professional asbestos sampling. I told them my plan and which walls I was going to remove and they only sampled the joint compound as well as the popcorn ceiling material. Test came back indicating zero trace of asbestos for all tests.

I'm a bit confused why they didn't care about sampling the wallboard itself. Some sources say that wallboard itself never contains asbestos, other say it may. What your thoughts? Should I get the wallboard itself tested? It's a "Westroc Firestop-6" wallboard.