Sigma used to sell many of their lenses back in the 80s with the fact that their lenses went the way of the official Retailer (sigma synchro II), how things change.
I ordered a Sony 200-600 today, it will be here tomorrow, however, I watched a lot of Youtube videos all stating how easy it was to move the distance ring and how it could be seriously reduced by using a lens coat type affair and slightly covering over the movement ring. I ordered one of those today and it should be here by Wednesday, I'll let you know how it works.