If I had to guess, it's because China is one of the most notoriously polluted countries that are also on the security council that will oversee this bill. While the United States and UK are pretty much guaranteed to veto, I think a lot of people are interpreting China as the swing vote here.

According to the article, Russia also opposes it in the current form. Doesn’t really matter since it’s non binding and there’s no hope of this being ratified by the US Congress.

Russia does not do anything of consequence without China's consent.