Here is my opinion:
Question: What are your thoughts on bow tuning by just using one bare shaft.
My opinion : I think it’s fine using one bare shaft, but you need to warm up as much as possible to make sure your release is good and clean, before you release the bareshaft!
Question: Would a bow be considered tuned if it would shoot a bare shaft straight and where you were looking?
My Opinion: You said would a bow be tuned, NO! The shaft would be tuned. I hate to be so technical, but you have to get the shaft tuned to the bow first, and then you fine tune the bow to the shaft: Such as brace height, string silencers, side plate, arrow rest.
Just my opinion, I could be wrong!
Hope this helps!