I saw an interesting NFL related thread about “following” a WR1. Basically said the reason we don’t do it, think it was Saleh, was that it means your field CB may need to now play slot. Your boundary CB has to flip to field. Your slot needs to know how to bump out to boundary etc. Essentially it’s not because your CB1 can’t do it. It’s because CB2 and CB3 can’t pick up the slack.
So the question becomes how able are the other 3 CBs to play other positions right now? And I think the answer is quite well. Sanders has been cross training. Gray obviously can. McKinney has plenty of boundary experience.