Why did they need to do an IQ test though? Grit is a completely different dimension.
Answers the question: low IQ, or low grit?
OP said he was successful without ever studying. That directly shows higher IQ, low Grit. Not sure what extra information the IQ test added except the vanity and ego boost it gives someone.
And this is precisely why I took the test. The only 'official' IQ test I've taken in my life. Psychiatrist told my dad I didn't have enough grit to stick with things I found boring. Guilty as charged. Fortunately grit did eventually happen, about 5 years later.