When I read that sentence, I gasped and thought the same thing.
I've spent a career writing thousands of lines of application code that would have never been needed if the database had been designed properly. But it wasn't because the deployer didn't think they needed "deep knowledge" that day.
We stand on the shoulders of giants who figured out the fundamentals just for us.
The worse the violation (different data types in the same column, ugh!), the more application code (10X) will be needed.
The more code written, the more more maintenance (another 10X) needed.
And none of it ever gets replaced, just migrated to something else years later (if we're still in business).
ASIDE: As for the interview question, I would never ask what "ACID" meant. I'm more interested in understanding than recall. I would just give the candidate a poorly designed database and ask what they would do to fix it.