They may not die, but they aren’t going to start crying if they feel bad. Many people don’t notice a chicken has a serious health issue until the chicken dies from it.
Even if you say your chickens are fine eating layer feed when they aren’t supposed to have it, doesn’t mean someone else’s won’t get a serious issue and die. It’s like walking on a train track. Sure you may not get hurt, but someone else undoubtedly will.
Mistakes are something to learn from, not to tell your friends it’s fine do replicate your mistakes. Just the next time someone asks if they can feed a non laying chicken layer feed, say they can’t. It’s really not good for them so they may not die, but it shouldn’t be done.
And btw if you know all your information from an old magazine article I would do some more research. A lot has changed since that was probably published and it is never bad to do some more research. Many people jump into chickens based on little information and it’s not bad, but it’s not ideal. Go out and do some more research and see what you find. It never hurts to know a little bit more on a subject.