I think I'd just go ahead and construe that ampersand as meaning "or". I mean, it can't really mean that everyone going in there must be female *and* changing a baby, so clearly one or the other is sufficient.

When I was a kid, I remember going into a clam shack on Cape Cod and seeing the "Buoys" and "Gulls" signs on the door, and standing there with my legs crossed until my grandmother came to see what was wrong.

Ever since then, I have hated and feared overly clever restroom signs.

I am just glad they clarified what the lower diagram meant.

It looked, at first, like something one would find on a restroom door in certain parts of Provincetown, MA (USA)