I'm sure I did mean to imply that it was an artificial construct, yes. Gender expression and identity are more continuous than people tend to believe.

For the interested, this seems like a pretty good overview of gender identity (primarily from a developmental perspective, of course):

http://steinhardt.nyu.edu/appsych/opus/issues/2011/spring/ge...

If the gender data is somehow critical to the data then it's worth being accurate. If not, why even ask?