I think it's a highly silly promise that they can't fulfil. Why? Because it's not on them, it's the DM's choice. There are as many straight/gay/bisexual/etc. people in a campaign as the DM chooses (unless I'm mistaken modules don't go out of their way to specify a NPC's orientation).
It'd be like saying that The Lego Group needs to put more gay people in your lego city.
It'd be like saying that The Lego Group needs to put more gay people in your lego city.