Answering truthfully — even when a flattering lie is available and expected — reads as attractive because it contrasts with people who default to telling others what they want to hear. Demonstrated via rapper Jack Harlow's interview answers: naming his actual romantic "type" plainly, and admitting he flew economy ("58C") rather than claiming a private flight. Source: [6 Flirting Habits Women Actually Love](https://www.youtube.com/watch?v=05vQ08uH-s0).
The appeal isn't the truth-telling alone — the source pairs each honest answer with a visible self-amused smile, signaling the speaker knows the honest answer isn't the one that was expected. That visible amusement is what reads as confident rather than merely blunt; honesty without it could just as easily land as tone-deaf.
Related: Congruence Principle (Words, Tone, Body, Eye Contact) (truthful words matching relaxed delivery vs. a performed answer), Verbally Own Your Experience (Naming Autonomic Reactions) (a nearby pattern of naming what's actually true rather than a socially expected version).