She doesn't say that Gender is a construct, she only says that boys and girls do not have excludingly binary tastes.
If Gender would be a construct, then that would also mean that Gendervarianted people do not exist either, and not the least, that Transsexualism doesn't either.
Speaking of it, by the way, It made me remember a mother of two, that had raised her small children in a gender-neutral enviroment as she did not wanted them to be "locked" in their expressions. However, when she one day desided to experiment by giving the boy a doll with a baby carriage and the girl a car, it ended up with the girl dragging around the car as a baby carriage and the boy trying to shoot away the doll with its carriage.