It's 53% straight and 45% bisexual (of whom 20% are men who date women and pre-op/pre/hrt transmen and 20% are women who date men and AMAB nonbinaries).

When I first encountered it, "demisexual" was very clearly a defense mechanism that girls were using to fight hook-up culture and the pressure to be promiscuous. They had to turn their sexual boundaries into an identity in order for boys to even pretend to respect them.