Probably not. However, pointing out what many may consider a minor falsehood could set yourself for an easy counter.

If Walker wanted to discredit your essay. He could give a sound bite like:

“Ok, yes, yeast. You’re right, but that’s not something most people consider relevant to sleeping rhythms. Haha. The essay is nitpicking minor technicalities but on a whole my research is unblemished.”

If I were his PR rep, I’d advise as such. You’re essay is too good to be vulnerable like that.