Well, CA is a liberal state. But our
cops are cleared of shootings vs non-functioning "firearms". If a judge allowed such a line as to supersede the reasonable man test, it probably wouldn't fly with the jury if there were any competent council to present opposing evidence. Our laws don't work like that.
In Britain or outside of the U.S., the laws may be that twisted. There, a reasonable man gives way to forceful criminals or faces charges himself. I hope that we have a clearer and more definitive understanding of what a reasonable man believes to be a lethal threat.
That said, the subject in the above story had a history of mental illness and may have been playing without any inkling that he was under police observation and never intended to threaten. The point is that officers are cleared in self-defense from what is actually a water nozzle. So expect one to be cleared in self-defense from what is actually a firearm.