I also believe it is used as a euphamism for any dating others in the program - especially since by doing so, a person can easily fool themselves into thinking they are working a program - but are instead just using the relationship/sex to distract themselves from working a strong recovery program.
There are predators in any vulnerable group... and newly sober alcoholics are no exceptions.
Also, another addictive behavior is sexual addiction. The program suggests sponsoring men with men and women with women to help protect against this sort of behavior.
After all, at most recovery meetings.... The odds are good. But the goods are odd.