Since youth level, Reece James has long been earmarked as someone to transition into a midfield role because of his passing ability, so I can see why someone like Tuchel sees his best position in our current system in the back three, because none of the other CBs have the same level of attacking threat.
The CBs in our system all need to be deep-lying play makers - able to switch play, cross from deep and shoot from range. At WB James only gets to use one of his attributes (crossing) whereas in that RCB position he'll be using three (passing, crossing, shooting from range).
The big downside for me, in an attacking sense, is the loss of James' big crossfield switches of play. Other than Ziyech we don't really have another player who is capable of switching the ball from right flank to left flank. It's an important consideration because of the success that Liverpool have had with Robertson and Alexander-Arnold switching the ball between them. It makes for a much more effective counter-attack because they don't need to pass back to their DM or CBs to switch the play.