None of them are the central figure of the whole game. Byleth is. Byleth is the POV character and exists in the center of the conflict regardless of the house choice made.They are the leads of their respective routes
Their roles in other routes doesnt change their leading roles in their own routes. The bloody stage is based off the school period so who gives a shit about their pts roles.
Claude, Dmitri and Edelgard are all on the damn boxart, taking more space than Byleth and are what everything in the game revolves around. Byleth is a non-character and no amount of spin is going to make him/her the right choice in a sea of white dudes with swords.
There are arguments to be made for diversity, but there was no way that Edelgard or Claude would be picked over Byleth simply for the reason that they're ultimately second fiddles in their game.