At this point "trap" has simply become shorthand for - at least as I've understood it - "deliberately presenting as the opposite gender", usually a male character dressed to look female. I wouldn't see an inherent intent to it besides fooling people into assuming they're the opposite gender. (Which makes it prettymuch cheating to use a Lalafell, but anyway.)

One of the first things I got asked when I joined an FC was "are you a trap?" (I'm not) and I'm pretty sure they weren't accusing me of anything.