It’s dodgy in that it’s a single personality metric. I know lots of very intelligent people who are almost entirely useless, and a fair few half wits who can turn their hand to anything
When you say that you know them – do you mean you consider them to be intelligent (or they are broadly held to be intelligent)? Or do you mean that you know their IQ score?
I’ve never done an IQ test, or been asked to do one or asked to do one* and I don’t think I know anyone who has or has told me their IQ or asked mine – so it doesn’t seem to be a measure that matters much in day to day life.
I could make the the same observations about people who are highly academic being impractical or vice versa but i don’t know anything about those peoples IQ.
* apparently eating the pencils and repeatedly throwing my own shit at my reflection in mirrors means I fail some sort of pre-qualifiction.