It is not about smoothness, laid back, lack sparkle, those describe tonality, not timbre.
I would define timbral accuracy as what lets us tell apart a musical instrument or voice, even when they are hitting the same note at the same fundamental pitch and loudness. In other words, does a violin sound like a real life violin on this earbud/IEM? Vocals and guitars are good in timbre on the TC200, but I do play in a band and I really find the stringed, brass and woodwind instruments on the Tingo TC200 is off, similar to a banned tribid piezo selling at $16 USD (non pro). Mind you these two sets have very good soundstages and imaging and technical performance, and have excellent price to performance ratio, and the target curve on the T200 is very nice, just that I'm a bit troubled by the instrumental timbre on it.
I think I'm just being nitpicky, and not everybody is particular about instrumental timbre and I guess it also depends on the music genres one listens to. Different strokes for different folks as they say.
But yeah maybe u are right about different drivers. They sell under Fengru brand also if I'm not wrong. Also QC is not the best in budget CHIFI as we know, so perhaps unit variation? I tried burning it in for a week, still same instrumental timbre. I'm gonna be giving away my TC200 soon to a friend, he listens to mostly EDM and rock, so maybe he can make use of it.