In my naval reading that’s not the way it works. You don’t move from executive officer to command of a capital ship, you learn command by skippering smaller ships and getting promoted to larger ships.
Care to cite the instance? I’ve read each series several times and don’t recall a 1st officer turning down command. Both Bush and Pullings were thrilled to get their own commands. And it was considered a compliment to the captain to promote his protege’s.