I suspect there are very few examples of it when they are as entangled and invested in them as Nvidia is in OpenAI.

no they don't - not when the lawsuit would affect the demand for the thing they're selling

There is a particular problem with this view. Yes, you learn how many lawsuits occur per year, but you are clueless on the base rate of actions that could potentially lead to lawsuits.

Is it a 1:10 ration, 1:1000, 1:100000?

You just don't know because companies don't tell you this information. If for example there were a magic oracle that forced every suitable action into a suit, would the entire legal system of the US instantly explode?