Please state in which country your phrase tends to be used, what the phrase is, and what it should be.
Example:
In America, recently came across “back-petal”, instead of back-pedal. Also, still hearing “for all intensive purposes” instead of “for all intents and purposes”.
The same goes for the exception that proves the rule. People use it as a magic spell that does away with unwanted evidence but it’s self explanatory. No parking on Fridays means you can park every other day.
There’s an exception to every rule (except that one)
That’s actually a post-hoc rationalization; in the original phrase, “proves” has a meaning closer to “tests”. But, yes, people use this one all the time to justify being wrong either way.
https://en.m.wikipedia.org/wiki/Exception_that_proves_the_rule
and how is that post-hoc?
If I claimed I didn’t get a ticket that day because I wore my lucky socks that would be post-hoc. I don’t see how that applies here.