Tis interesting, the way it throws our ideas of gender for a loop, lol.
But the fact is that the basic male or female division isn't always as clear cut as most people assume. There's a lot of reasons why those whose gender is a little um, fuzzy, maybe? have always kept it hidden, but it's always existed.
As to why he'd choose to keep the female 'plumbing', I suspect that's easy: because he could, lol.