@jck51 Please understand that members of Mayo Clinic Connect are not medically trained so we often don't really understand whys. We are all patients of a Dx that is confounding even to the doctors treating us. PMR/GCA/vasculitis are all uncommon to rare medical problems with limited knowledge professionals available to treat us.
I can not get a consistent answer when I ask just two rheumatologist. I have a treating doctor where I live and I have a 2nd opinion Rheumy who works with a different teaching hospital in a different state. Some days I'm not sure they would agree on sunrise in the East vs. West.
As far your question on Inflammation markers while on an IL-6 biologic. I asked my AI tool and it dumbed it down so I could understand. They are indeed not reliable when on Actemra/Tyenne. Possibly you use an AI tool and can query it. I have learned to change the question I ask if my tool doesn't answer my question on the first try. You can also try doing a simple internet Search -ask Dr Google.