Yet in this case, nuChekov is explicitly a different person altogether - born four years later than his TOS self. I was just commenting on the fact that Uhura is another character who in theory could
be a completely different person biologically (she's the physically least matching casting in the troupe, at any rate), whereas Kirk, McCoy and Spock could not be biologically different by story logic.
Typically, when a character is recast, we're not dealing with splits in timeline. In this case, we explicitly are...