Oklahoma v Castro-Huerta is a ruling in favor of the state

[Dereich]

Kavanaugh likely writes a decision in favor of Oklahoma.

Nothing in your link indicates that this is the case.

[Dereich]

Kavanaugh is the only one who hasn’t written anything from the April sitting.

So? Its not like its a rule that they should be spaced out among justices. Plus there are plenty of other big cases remaining that he could get over an April one; I think he might get the EPA case if they don't want to let Gorsuch end Chevron deference. Plus, even if they did want to give him something from April, Biden v. Texas is still available too.