Frankly, I always thought that Madeleine's children should be plain Leonore Bernadotte-O'Neill, Nicolas Bernadotte-O'Neill and Adrienne Bernadotte-O'Neill. And CP & Snakey's children shouldn't have titles either. (Alexander Bernadotte, etc.)
IMO - All the Prince-n-Princess titles and the granting of Duchies is a waste of time and energy (and an exercise in pomposity) to children who will have nothing to do with the Swedish RF or its duties.
I think the problem was that at the time, Leonore was the spare. I don't think there is such a gap between Estelle and Oscar on purpose, and Snakey and CP weren't married yet. Of course, once they'd given Leo the titles and Duchy, they had to do it for them all. I think if there was a spare from either Vik & Dan or even Snakey & CP before Leo's birth, they'd have been untitled.