Are we getting dumber by the hour to need a tutorial on how to use a knife?
Combine that with dark restaurant lighting and the need to not seem like an idiot around polite company, I don't think I would personally clue in right away that I need to hold the knife opposite to every other steak knife I've ever used, nor inspect it close enough to realize the cutting edge is on the "back" in front of people who will think this is the first time I've used a steak knife before or something.
If you're not dumb, then you would figure out how to use the knife after taking a look at it and seeing which side is the sharp one.
That's almost textbook intelligence; being able to resolve abstract problems based on limited information.
not investigating something = being dumb
You can just ask if you aren't sure. If I welcomed you into my house, and asked you to turn on the lights, while not telling you it's wired in a three-way switch config where another switch has to be turned on first, I think the dumb solution there is flicking on and off every light switch for 5 minutes till you get it, rather than just asking me. To me, holding the knife up to my phone's flashlight, or gently grazing the side against my palm has the same sort of "why are you doing that" energy everyone wants to avoid.
Dark restaurant, social pressure to not do weird things at the table, I get why anyone could mess up.
After reading the design of everyday things, I no longer blame that stupidity on me...