Thrall wasn't the front runner of Battle for Azeroth and yet you've brought him up before. Kyrestia as a covenant leader would hold the same position of a major lore figure. Sylvanas was also covered up in Legion. She wasn't "fronting" the expansion but did become the Warchief. Again you try to move the goal posts to a painting that was changed into a bowl of fruit.
The only trend you have pointed out is that characters get model updates as they become important to the story even when they are not "fronting" an expansion. That isn't sexism it is just updating their models for their importance to the story/scene.