Everyone has different shaped ears. Who would know if someone would have an ear that is shaped the way you could say theirs doesn't cause a change? Are medium sized ears more neutral? What about the internal parts of everyone's ears? I'd imagine they're all different too.
I think the important part would be that everyone needs to use live music for a reference. If their ear shape makes it sound bright/colored (that is being assumed here) ,it still would be normal for them. When they hear that same music on a system, their ear shape will still most likely be able to know if the reproduction matches that live music.
If anyone else with any ear shape/size does that same test, they're going to hear those changes too.
I think they can recognize a bright, or dark colored system, since they still will know it's different from the live source itself.
So I would say it shouldn't matter. Using the source for a reference is what is important in my opinion.
I think the important part would be that everyone needs to use live music for a reference. If their ear shape makes it sound bright/colored (that is being assumed here) ,it still would be normal for them. When they hear that same music on a system, their ear shape will still most likely be able to know if the reproduction matches that live music.
If anyone else with any ear shape/size does that same test, they're going to hear those changes too.
I think they can recognize a bright, or dark colored system, since they still will know it's different from the live source itself.
So I would say it shouldn't matter. Using the source for a reference is what is important in my opinion.