I agree it depends heavily on the IEMs being considered, but I think differences in dynamic capability can result in large audible differences in IEMs with similar tonality, even if they're from the same manufacturer. The only Moondrop IEM I've heard is the B2Dusk, but I've seen reviews describing the S8 as smooth and lush while I've never seen any reviews describe the Variations as such. It seems to me that the S8, despite having similar tonality, is better with microdynamics (more precise control over small volume changes) leading to audibly smoother transients, more audible texture, and deeper soundstage (perhaps at the cost of some raw clarity). If anyone in this thread has both IEMs, please feel free to correct me.Ok granted, what I said before, if IEM 1 has much faster transients than IEM 2 with otherwise identical FR, there would be a difference in the dynamical rendering, but the overall sound characteristics would remain the same. And in the example discussed above, I doubt that there is such a huge dynamical difference resulting in large audible differences, i.e. Moondrop S8 and Variations should sound very much a like, the Galaxy Buds+ might be a bit more sluggish and thus not that resolving.
This kind of stuff is also heavily on the person listening. Some people are going to be more sensitive to hearing these kinds of differences and some people just aren't care about these kinds of differences because it doesn't directly impact their enjoyment of music. But it definitely matters to some ears.