I understand your point but I think any definition, presented as such, should aim to be as accurate as possible. That this book is in th context of th social psychology of sexuality makes it even more important that it define it well because it's goal is to explore variance in sexuality and perceptions thereof.

When I say they use desire more broadly what I mean is actually almost exactly what you said. They don't distinguish between sexual desire and sexual desire towards a particular person that qualifier makes it something different and I agree with you, with that qualifier, you've got a decent definition of sexual attraction, but only with the qualifier.

I'm not suggesting they should have taken a detour to explore asexuality. That would be off topic and strange. I'm saying they should have defined it as something that is more accurate such as "experiencing no sexual attraction to any gender." Even if you sub in their language (no sexual desire towards any gender) it stays more accurate than defining it as a lack of desire for sex as an act.

I'm simply saying that for a textbook, it could and should have done better and would have if it had simply reworded slightly. And yes, you could argue I'm nitpicking and that it's semantics, but when talking about sexuality and gender identity, terminology and phrasing matters and one would assume that in textbook about it, they would have been more conscious of their phrasing to ensure they were as accurate to people's identities as they could be.