I think a lot of what you're saying about her "aggressive" pronunciation is H!P tradition and required of her by the director. Which is not to say that your analysis is wrong, just that I think she is that way for one specific reason.This girls voice is amazing for an idol. Such control and warmth to the sound. She is a bit aggressive in her pronunciation, but that can be improved with time. I see such promise in her voice. She does need to practice being just as dynamic in her quiet times as her loud times. She also needs to smooth out her transitions from note to note, adding more "legato-like" or "glissando-like" motions to her singing would make her untouchable, in my humble opinion of course. She had minor intonation issues when singing accapella, but those happen to everybody. For a young lady, she shows much promise.
The story I tell myself is: Tsunku was aware of how little attention is paid to backing-tracks among idol fandom, so anything he wanted to accomplish rhythmically had to be right in their face, (coming out of the idols' faces). So, he made it "a thing" for everybody he raised, and the later, additional singing coaches, voice-directors and overall producers took it on, both as "The H!P sound" and the already present singing style of some proportion of their talent.
For my part, I've long been curious what all of the better singers in H!P would sound like if they were given instruction to sing more like Western idols or mini-divas.
