I totally agree with that. It was Kajiura's heart and mind and view of the song/world that we heard in Kalafina. I guess we get to hear a comparison/"composer cover" view of those old songs. Kajiura wil be "covered" as well in trying to replicate her vibe by the instrumentalists/musical direction...
Maybe she can just go deeper musically and use her heavyweight vocalists more directly, instead of depending too much on Kalafina's music to draw fans. I mean, we were talking not long ago with
@grunty schooling me that Hanae would ne excellent to sing lead Wakana's part in Oblivious (which I've actually warmed up to a bit more), but who knows what the mighty fans would say (even knowing that it's a COVER)! "She's too solemn and not exciting like Wakana - give us LINO LEIA!" (I don't hate LINO, I've supported her on this forum. She's just in the crosshairs, indirectly).
She's able to vary her vocal tone and colors by changing her resonance placement, and also stylistic changes frequently. I think it's an expressive palette she has that the J-audience who complain may not be board with, at least in comparison to Wakana's mostly straight singing.
Wakana on the other hand often sang forward and sweet and had a strangely forward but mournful voice. She also sang with much less dynamic variation (messa di voce) and tended to sound the same continuously, only sounding tonally different when she sang quite low (getting breathy), or did falsetto/head voice (much less stable). She did use the cry effect for emotional expression, which laid on her mournful core must make people weep at her singing (LOL).
Well, watching videos of one Japanese guy on YT that interviews half-Japanese ladies in Tokyo (which Joelle actually is, anyway), I've heard it commented on his videos that the same person speaking in Japanese would have a higher more forward tone with Japanese mannerisms, and speaking in English (or other European language) would have a chestier, more grounded speaking tone.
I just watched "my long forgotten cloistered sleep" from YKL 20, and I didn't get the idea of Joelle singing "heavier and chestier" since the song is a high-range song in the 4th and 5th octaves (C4-E5 it seems) so there's more use of lighter chest-mix and head voice. It doesn't seem like anyone should have a problem with Joelle's take, since the song's range means it's placed higher/potentially brighter by default. In fact, Joelle's voice sounds similarly placed to Wakana's on the first syllable, "In" and also on "was" on the first line.
"fiction", on the other hand, was placed lower and more in Joelle's chest range. (I wonder how Wakana's voice would sound singing that song...). So, of course, Joelle took it more darker for impact/effect. I think that more closely fits the "chestier" description you gave.
I mean, for comparison, Eri does not sing poppy. She has a full voice and no one complains about her Japanese singing, though her voice is more forward placed and brighter than Joelle's. I have a feeling those J-fans that don't like Joelle wouldn't like a singer like MIKI MASUDA either, since she's more jazz/rock influenced, though not English speaking, and she also does some stylistic/resonance movement in her singing.
I do agree that it was something special, though many fans tended to diminish Keiko's role always just praising Wakana, and some even said Keiko is nothing without her, or something to that effect, which I always challenges.
Evidence of this is that in Wakana's solo lives, the Kalafina songs sounded weak and flat dynamically without Keiko's voice, not just harmonically, but tonally with the instrumentation. The true test of this "perfect harmony" would be to have them sing their popular songs acappella.
The massive foundation and pillar of the music as written and performed by the FBM is also often taken for granted. We heard this when Keiko did her solo live with other musicians and needed to bring in Konno Hitoshi to play violin on one of her solo songs that didn't include a violin before, just because the musicians/arrangement was not of a sufficiently high standard to give the desired live effect.
Kajiura's musicians are top-notch too! The FBM is a high-level unit with their own common language in playing together for so long.