What the above posters have said. But I've always figured even with perfect derailleur and adjustment, it can be just the way mechanical stuff works sometimes: there are limits in which it works well. In this case, not big-big or small-small. There's really no reason to use those combos, just don't use them. I can't give you specific examples, but over the years with various drive trains and bike frames, I've had derailleurs that rub in the extreme cross chaining. I've adjusted as best I can and then just chalked it up to it being the way it is, it seems logical, and I don't bother chasing it down or obsessing over it.
Last edited by Camilo; 03-22-23 at 11:20 PM.