Eh judging a persons entire intelligence on a single gap in their knowledge, particularly trivia that isnt particularly useful, is a bit disingenuous is it not? I just have the phrase 'verb is a doing word' that i remember a teacher saying at some point in my childhood, thats the only reason i remember that and i have not once needed to remember that at any point in my life. It is good to be taught it as it helps you understand the mechanics of your language, and knowing that probably has helped indirectly in other aspects of my life, but i wouldnt put someone down too hard for that one single gap.