The coinage of sex-love was designed to distinguish the increasingly prevalent, publicly lauded middle-class hetero-erotic amour from that class's old, spiritual true love. With the inauguration of sex-love, the erotic attraction of men and women was now supposed to lead to love which led to marriage which led to sexual relations - which might, or might not lead to reproduction.
As radical feminists saw it, women's problem wasn't just due to prejudice or misunderstanding and so wasn't solved by reeducating the bigoted or misinformed. Women trouble was built in socially, a culturally structured inequity.
The dominant social usage, say the writers, distinguishes a "lesbian" from a "woman." This implies that a "real woman" is dependent on a man. A woman not dependent on a man is not a "real woman."