I don't think that's really true as a general rule. Passing a variable of an unexpected type or nullable could have completely unpredictable behavior depending

I don't think that's really true as a general rule. Passing a variable of an unexpected type or nullable could have completely unpredictable behavior depending on what assumptions the code makes about the incoming parameter. It could have no effect or a catastrophic one, there's really no way to know without reading actual code.