These covers are terrible.
No uniformity or anything close to that.
You mean the cover selection or the recordings? I feel like the recordings are a bit off, but I can't quite put my finger on what.

I can hear Chihaya strain her voice occasionally, such as in Nemurihime. I feel like that's the most tired her voice has ever been. The song's melody wandered around and the build up was weird, so I didn't really enjoy it.
That was recorded after her CD had been delayed for a week due to Mingosu having voice issues, so that's probably why.
That being said, she has more hits than misses. I really can't hear what part of her voice is supposed to be "whiny". Chihaya's voice is usually pleasant to listen to - I didn't hear anything weird in Good-Byes, 99 Nights was great, Saihyou was absolutely stunning. The only exception to this was edeN, where she did sound quite weird. In most happy and passionate songs Chihaya's at least decent.
Yeah I'm accepting that these recordings aren't all done at the same time and each idol has their off days at times. Before OFA I had expected to like her version of edeN most of the Shiny Festa songs, but ended up liking her Visionary most.
https://www.youtube.com/watch?v=phqRwKlTpOoThis also can happen with in game versions compared to master versions. For example I didn't like the previews of the master versions of the new solo songs compared to the in game versions, but it could be I'm just not used to them yet. In the past some songs took a few listenings before I enjoyed them.
What surprised me when reading voice opinions on another thread is that many consider Haruka's voice to be "adaptable". I really don't understand why. Haruka's voice sounds thin and "brittle" most of the time. She tends to miss notes (or at least hit them weirdly) much more than Chihaya because her voice cracks. For example, her brute-forced Overmaster sounds downright awful. You can always hear her struggling with transitions and she just doesn't have enough power to maintain strong notes. I can understand if someone were to call Haruka's voice "whiny" (although I like Haruka, that's something I'd accept), but I actually can't hear any of those qualities in Chihaya's voice at all.
I'm also sometimes surprised by what some people say about the idol's voices. Speaking of Haruka I prefer Chihaya's version of I want, mostly because it sounds more forceful I guess.
https://www.youtube.com/watch?v=xqFLt-NyGuII think Chihaya's range is pretty good, and it's only gotten better since the beginning (although some of those tracks were recorded uncutely on purpose). I feel like even if she can't vibrato like Azusa, she tries to make it up with her power. Her specialty tends to be strong long notes in my opinion.
So in the past she had an issue where she was always singing powerfully even on songs that didn't need it, but I feel like this has changed a bit since OFA with songs like Kimi Channel and 99 Nights (where in the latter she changes between loud and soft constantly).
https://www.youtube.com/watch?v=2dWVrc-Bfs0https://www.youtube.com/watch?v=KGit9y4M8dwAs for strained, I was surprised how high the notes got in Saihyou.
https://www.youtube.com/watch?v=blJgHVtxu8QI haven't heard like Chihaya was straining herself, but maybe I'm just missing something.
As a side note - I do like Haruka's voice when it's soft and smooth such as in Looking for Love, Kosmos Cosmos, Me ga Au Toki, and parts of 99 Nights.
Another thing is I don't value singers just on objective quality. I also consider more subjective things like how they fit the song or other things in their voice. For example I find that some of Haruka's songs and covers are comforting to listen to because it's her voice.
https://www.youtube.com/watch?v=WuXMS-DlSQk