Yeah no doubt Yamazaki's vocal here is straining, which only accentuated the roughness quality. And trying to sing a fast tempo pseudo-rock song (keep adding "pseudo" as a caveat 'cos I can't help myself, lol. Am not a rock purist or anything.) intended for a group and on a key that is probably a bit higher than comfortable for her natural vocal range certainly didn't help. Her performance was fine; just nothing really exceptional which is probably why she didn't win despite all the pre-performance buzz, if I have to guess.
My describing her vocal wasn't a critique of her performance here, but pointing that she won't be a Kamikokuryo vocal type with skills that I've been waiting since...Matsuura maybe (within UF), which means quite a while now. Again strictly personal taste in this regard.

There is a reason why Kamikokuryo isn't really a vocal ace even within her own group and never seriously considered when invoking the best H!P vocalist shortlist - still like her vocal just fine btw.
So what if hers is lacking skills and one-dimensional - it's very rare type of vocal color, especially within H!P as I can't think of any. Her type of strong/high vocal is of a quite different quality when compared to so-called "high pitch" vocals like Maeda Yuuka and some others, if i may add. It's strong/clean vs soft/weak.
Based on what I heard (of Yamazaki's few performances), she can hits/belts notes a bit better than most, which is why folks are considering her to be the next big thing. She isn't quite Dambara-level, but probably more close to Murota and better than Kaga/Hamaura when strictly talking about debut-ready Kenshuuseis IMO.
A bit of off-topic, but not sure how many folks watched when Music+ (ep73) featured Suzuki+Okai recording the song a while back. Putting in a spoiler as it's getting off topic again.
One can clearly hear Okai is straining big time while Suzuki is hitting notes relatively easily during the chorus part. It still kinda works as it's a rock-feel and she has that vibrato going - you can hear them commenting "ぎりぎり" during Okai part. These two have a similar vocal range though and Suzuki doesn't strain/crack as much usually as she sings more of mixed voice for those high parts - while Okai is almost all from chest voice. So during live performances, Okai will crack way more but always will louder and more powerful. I've usually preferred Okai's over Suzuki's - no doubt that Suzuki is a better singer, has better control of her vocals, can do falsetto the best since Matsuura within H!P that I've heard (gonna ignore girls like Ruru since it was just that one song and it wasn't that good IMO, ditto for Kago), arguably better mid-tone, the list goes on. Pretty much the only thing going for Okai is that Suzuki still can't really do vibrato and Okai can sing louder. But Suzuki's vocal has this habit/tendency that just gives out on end of phrase on high notes that have always bothered me. While some can hear it as a style and don't hear much fault in it, I've always felt it made her sound a bit amateurish, every time her voice just give out on notes. Having vibrato and something to properly finish notes on some of those will go a long way, but again IMO.
Anyway where am I going with this before getting more and more off topic...I guess I was trying to write that with practice and age/experience, one can improve - to a point. I remember Sakura (around her MM debut period) straining quite badly for higher notes but these days it's not as bad. It's still there but not as terrible as before. It's never going to be the same quality/color on those high notes of Kamikokuryo/Matsuura but that just becomes a strictly personal taste category after a certain point. So it's not like I've already abandoned the Yamazaki Yuhane ship.
