gender and sex are two different things, although often aligned. i'm not sure that i agree with what these parents have done, but i'm not sure that i completely disagree either. there is something to be said for self-identification, and the more we categorize children from the outset, the less they are able to self-identify.
we didn't know the sex of our first child until she was born, and the vast majority of clothes, toys and baby-stuff we had accumulated and that we used in her first 18 months was green, yellow, orange etc. i put her in blue rock and roll t-shirts and jeans, and she played with all manner of toys when she was old enough to do something besides eat, sleep, poop and puke. with all of that, she very firmly decided, as early as she knew what colour was, that pink was her favourite, and that she loves bunnies.
that may be something, and it may be nothing.