It's completely reasonable for the establishment to reject a request for an alcoholic drink, and suggest something alcohol-free instead.
It is not reasonable for them to say "sure, here's your alcoholic drink as you requested" and give them an alcohol-free substitute without telling them.
The fact that the patron broke the rules has nothing to do with it.
Your analogy doesn't work because: - they tell you the rules at the entrance of the bar - they totally tell you when they give you a substitute
The only issue is the bartender asking you for your money before serving you the drink really but again, this is known since day 1 by the customers.
"This is alcohol"
And
"Or maybe it isn't alcohol."
Or to rephrase it, "They tell you the rules at the entrance, they then tell you they don't follow those rules and they are totally serving alcohol even if they are not."
You can decide you are okay with that or not but they aren't dishonest. I wouldn't enter that bar personally but if you do you cannot really complain. It is like complaining because you haven't won at the casino.