Three points there:

1. Power of Syberia 1 throughput is not fully utilized.

2. China pays half of the EU price.

3. Power of Syberia 2 not be build in the near future. It's not the deal to actually do something. It's too continue further discussion.

Russia selling gas to China is completely orthogonal to Nord Stream issue.

The strategic win in bombing Nord Stream was that Ukraine finally got Europe on their side. Before NS was blown up many countries, especially Germany were sitting on the fence, reluctant to give Ukraine any help. They were hoping for Ukraine to lose the war quickly, then they would give Putin some slap on the wrist punishment, and return to "business as usual" with Russia. Nord Stream being destroyed removed the biggest incentive for doing that.

The devil is in the details. The conditions that China wants aren't very lucrative to Russians, and the second pipeline, if it is even built, will take about a decade to build, so not "now".

Russian negotiating position is weak and Beijing knows that.