In the past, I have thought to compare this with ?? ???? ??? ?? ?????, as we see by other ?????? ????. I do not know the ins and outs of Avoida Zora, so I can’t be sure I am right with this, but the way the ??????? explain the ???? of ?? ???? ??? ?? ?????, I don’t know if you can apply it to Histaklus; it would only be by ?????? ????. See ??’ ?’ ????? ???? ????? ??’ ?”? ??”?. (Yes, I know not to pasken halachah from a Chiddushei R’ Shimon!)
A friend of mine recently showed me that the ??? ???? does apply ?? ???? ??? ?? ????? to the case in ??? ????; (http://beta.hebrewbooks.org/reader/reader.aspx?sfid=14233), although he explains that Arayos is worse.
Perhaps that’s why there is a ???? ???? here; it’s anyways technically ???? because of ???? ????; it’s only the ????? ??????. Dunno.