Stop being so defensive.
Your point was the best Sox outfields have always had a RF capable of playing CF. Dwight Evans was a RF on what has to be considered one of, if not the best, outfields in this team's history, with Rice-Lynn-Evans. Hopefully you can agree Evans never established himself as a capable CF and his defensive abilities out there are at the very least, in question. Right? His defensive abilities in RF are without question - one of the best ever to play the position in MLB.
So beyond this season where Betts has shown himself to be play RF and CF well above average, I wonder what other Sox outfields you are referring to. I am not so sure I can think of any other great Sox outfields where the RF was a even a capable CF, unless you were referring to Ramirez-Damon-Nixon, which was a good OF, but certainly no Rice-Lynn-Evans.
Maybe Gomes/Nava-Ellsbury-Victorino? Certainly Victornio was an excellent CF before playing RF in Boston. But I would be very hesitant to rank taht among the best outfields on thjis team. Although they did win a ring, which shouldn''t be ignored. But I'm not really sure what outfields you were referring to...