Btw, as someone who always watched columbo in italian, I have to say it doesn't come across this way in the italian version: brandt asks him "tenente, non ha mai pensato di cambiare professione?" "lieutenant, have you ever thought to change your line of work?", and he answers "no, mai, non saprei fare altro" "no, never, I wouldn't be able to do anything else", implying he knows how to do ONE thing very well and that is being a detective, so at least in the italian version there's no hidden meaning.