I read that verse twice, and it seems like only male homosexuality is emphasized as being unseemly and really disgusting. The thoughts and feelings on lesbians is vague and kind of left open to interpretation.
I've always wondered why that was never fully dealt with. It could be that even though there were no "male or female, jew or gentile" in the new Christian church, the role of women were still seen as subordinate and in theory less vital than the roles of men. Therefore, their activities might not have been of the utmost importance to St. Paul.