It’s a descriptive rule, not a prescriptive rule, and likely one snuck into the powerpoint to try and get the class thinking and laughing. Like calling the descriptions of gravity the “laws of gravity”, it describes something about the world we’ve seen, but there’s no Physics Police enforcing all matter follow the “Laws” - it’s just the term we use for a description of how things work.
A lot of advanced English classes are much more on the descriptivist side of things - observing patterns in ways we use language - than the prescriptivist approach we get in grade school where we’re just learning rote things like spellings.
It’s a descriptive rule, not a prescriptive rule, and likely one snuck into the powerpoint to try and get the class thinking and laughing. Like calling the descriptions of gravity the “laws of gravity”, it describes something about the world we’ve seen, but there’s no Physics Police enforcing all matter follow the “Laws” - it’s just the term we use for a description of how things work.
A lot of advanced English classes are much more on the descriptivist side of things - observing patterns in ways we use language - than the prescriptivist approach we get in grade school where we’re just learning rote things like spellings.