DY, it is possible to dress differently on dates, but if I can generalize, I would think a guy who asks about tznius is not looking for a girl where its a question and vice versa. It would be just as smart as a reference trying to “help” someone and lying about tznius/hashkafa level etc which is a horrible recipe for marriage.
The story you mentioned involved lying (or very direct misleading) and I wouldn’t equate that with handing over a question to someone better equipped to answer it. I would certainly agree though that where one has concrete negative information Halachically allowed or required to say, a person should make sure the question is answered one way or another.