I don't know why you're over-complicating this. The body that decided on that terminology didn't even invite Taiwan to participate. The terminology was chosen at the behest of China. That body was obviously not neutral.
Once again you're over-complicated this. The organization could have invited Taiwan to participate and asked them what they'd like to be called. That would certainly satisfy those questioning the organization's neutrality.
Allowing the PRC to decide what the lands they govern are called and allowing the ROC to decide that the lands they govern are called is _obviously_ more neutral than allowing either the PRC or the ROC to make the decision for both sides. Taking the PRC’s side (as that committee did) or the ROC’s side is basically the definition of “not neutral”.
China does need to be “satisfied” for it to be neutral.