He kind of highlights why she couldn't be Queen though. The people around the throne look down on those without magic, and she doesn't have magic. Her research into magicology was only possible because she gave up her position as heir and devoted her time to it. If she had stayed as heir, her duties would have prevented her from attaining the power she now has, and would have been the puppet herself, with the people around her claiming how he would be the better king instead.
She only makes for a good Queen because she refused the role in the past. If she had held on to the position of heir, he'd be working to usurp her for not being fit due to her lack of magic. He's just salty that she started from a position of weakness and built herself up without help to surpass him.