The main point is - it's a intrinsically a footgun question (a stealth behavioral question that also happens to have no rationally correct answer). Quite plain

The main point is - it's a intrinsically a footgun question (a stealth behavioral question that also happens to have no rationally correct answer). Quite plainly there's no rational reason for someone to suspect that in this particular case of a standard boilerplate HR question ("How do you rate yourself?") that they should expect your secret trapdoor answer ("4 or below") should apply rather than the usual, automatic "7-9 is the only right answer"). I'll take your word that it wasn't intended as a joke. But it was intentionally oblique and slippery. All that you accomplish with a "filter" like this is to flush a lot of otherwise potentially perfectly decent candidates. And if they were to find out after the fact that this was where they "failed" your interview (after taking a whole day off work, driving down there, and going through all the other interview rituals) -- they'd be perfectly justified in applying whatever 4-letter words came to their mind in regard to that company and its vaunted "culture".