That phrase doesn't refer to anomalies, it refers to signs that says "no parking between 5-10pm". It implies the rule that parking is allowed otherwise.
"The exception that proves the rule" is a saying whose meaning is contested. Henry Watson Fowler's Modern English Usage identifies five ways in which the phrase has been used,[1] and each use makes some sort of reference to the role that a particular case or event takes in relation to a more general rule."
duckduckgo search assist: The phrase "the exception that proves the rule" originates from the Latin legal principle "exceptio probat regulam in casibus non exceptis," which means that the existence of an exception indicates that a general rule exists. This concept suggests that if an exception is noted, it implies there must be a rule that applies in other cases.