פירוש על עבודה זרה 117:5

The three practices that R. Hiyya sees are what I would call “marginal.” The women are not becoming pregnant from non-Jews. They are having children with non-Jews who seem to have converted, but not done so according to rabbinic law. They know that conversion entails circumcision, but they do not know about immersion.
They are not drinking wine made by non-Jews. They seem to know that this is prohibited. But they do not know that it is also prohibited to drink wine poured by non-Jews.
They are not eating non-kosher food. They are eating lupines, a type of bean, cooked by non-Jews.
All of these are what I would call infractions of rabbinic law, practices that many Jews may simply not have known about. They are also all intended to keep Jews from fraternizing with non-Jews.