After 10th gen, I've always justified his choices as fulfilling certain ideas, rather than being girls that "are ready". Probably rather something that the group lacks, or might need in the future. Like how Haruna fulfilled the stylish and more mature role within current Morning Musume. That's also why we have back girls, they're the underdogs you want to support and find charming because of their efforts. Even aces, develop, and change, and that's one of the charm points of Morning Musume.
So I'm curious for Tsunku's comments on this and training camp footage. I'm glad we didn't get footage otherwise we'd have more "Kikkas", so we get more focused footage on the winners instead.
I wouldn't be surprised if the two kenshuusei was an executive influence because there's so much kenshuusei right now that surely by now they're amounting a profit off these girls, as its marketing for the trainees.
I've forgotten how in this video it looks like Maria has vocal potential: