Not all stages have safeties built into them. Many don't today, and many more in years past didn't either. And cameras fell. Very likely, it was the cameras falling that led to someone at some point designing a safety into the stages. I'd bet, however, that never did an operator become angry with the manufacturer for not protecting them from improperly mounting a camera.
That's interesting, I always thought they had them built in.
I'm taking it over to Tiffen on Monday, looking forward to what they say as well.
Thanks again for the responses and allowing me to vent a bit. This is a great Forum!