They didn't do it voluntarily. If they used China cotton, they would be the target of western campaigners and boycotts. If they don't, they get the same in China.

They were in a lose lose situation. They lost.

Could they have done better? I think so. They could have made a claim that all items would be labelled so consumers could choose. Or they could have said nothing sold in Europe/the west contained Chinese cotton.

But that compromise might have just gotten them boycotted in both places.