In 683 Obito said that Naruto Bunshin's chakra wasn't enough for 2 Kamui. So he needed Naruto to jump in and Sakura to jump out. And that's what's been happening.
But... Back then, Obito was talking about Naruto's Bunshin who had 50% of Naruto, Kurama, Hagoromo and Nature chakra. But in today's...