Let's pretend that you're limited to just reading press clippings and forum posts about modern fighters, as people were limited back in the day. Would it put you at a disadvantage when picking fights' outcomes? Or not?
It would completely depend on how you were at picking fighters apart by eye. If you were good, you would be at a disadvantage, if you were not good, you would have an advantage.
We will assume that the person would be equally skilled at picking by eye and through press clippings.