It can be pretty straightforwardly interpreted as a reference to the probability of being born into one gender or the other, which is roughly equivalent to a coin flip (not taking into account the higher chance of being born male, hermaphrodites, etc.)
I have trouble grasping why this distinction matters.
My understanding was that when people make "If I were X" statements, they are referring to having a conscious experience different than what they are currently experiencing. They would still be themselves by virtue of being the conscious observer in that context.
There's far less than one chromosome's worth of difference between me and a orangatan.
"Just a chromosome" is like saying "just an extra brain"