What if it is a pareto improvement: better improvement for some dialects but no worse than the earlier version for anyone. Should it be shelved or tuned down so all improvement for each dialect see gains by an exactly equal percentage?
Do you think we should keep using that codec, because overall we get a better sound quality across all groups? Do you feel the same as a member of group X?
Your same argument can also be used to degrade the performance for all other groups, so that group X isn't unfairly disadvantaged. Or, it can even be used to argue that the performance for other groups should be degraded to be even worse than group X, to compensate for other factors that disadvantage group X.
This is argumentum ad absurdum, but it goes to show that the issue isn't as black and white as you seem to think it is.
And if their contribution was to the final system, sure, it's the owner's choice what the threshold for acceptable contribution is. In the same way they can set any other benchmark.
> Your same argument can also be used to degrade the performance for all other groups,
The context here was Pareto improvement. You're bringing a different situation.
I suggested that the same argument could be used to say that we should actively degrade performance of the algorithm, in the name of equity. This is absurd, and illustrates that the GP argument is maybe not as strong as it appears.
Changing codecs in practice takes years/decades, so you always have time to stop, think and tweak things.
If improving the codec is a matter of training on dataset A vs dataset B, that’s an easier change.
If the codec has the intention of working best for human voice in general, then it is simply not possible to define sensible subsets of the user base to optimize for. Curating an appropriate training set has therefore technical impact on the performance of the codec. Realistically, I admit that the percentages of speech samples of languages in such a dataset would be according to the relative amount of speakers. This is of course a very fuzzy number with many sources of systematic error (like what counts as one language, do non-native speakers count, which level of proficiency is considered relevant, etc.), and ultimately English is a bit more important since it is de-facto the international lingua franca of this era.
In short, a good training set is important unless one opines that certain subsets of humanity will never ever use the codec, which is equivalent to being blind to the reality that more and more parts of the world are getting access to the internet.