People don't think that rigidly or uniformly. Straight meant opposite genitals AND opposite apparent gender. If one or the other was violated, many would consider things not straight. Some did think it was only genitals, but many would disagree. Just like how white supremacists will say Jews aren't white, conservatives would identify either same genitals OR same apparent gender as not being straight, even if many people didn't. Some people might have considered apparent gender to matter, and genitals to not.

They'd all use the same word, but mean different things. That's why "American values" means liberal democracy to some, Christian nationalism to others, unregulated capitalism to many, and a combination of the three to most people. They all think they're in agreement, but in reality they aren't.

Language is always fluid and inconsistent; allowing room for semantic abuse. It's how fascists bind an unpopular idea, like queers being pedos, to the more popular idea of us grooming kids into being queer. We don't make people queer either, but it's a more common of belief that can boost the popularity of us being pedophiles through the vague word "grooming." If someone accepts that we groom children into gayness, they might spread the term groomer, or internalize it and start to believe we groom kids in other ways.

White could just mean skin color, but it wasn't only used that way. Straight sometimes just meant genitals, but it was also used to other people that didn't fit in for just as long.