Precisely. Trump is trying to do Bush-style Triangulation here, and it never works.
After reading the memo, it seems pretty clear that the intent is for Sessions to conclude (rightly) that firearms with bump stocks are not “machineguns” under any reasonable reading of the NFA, and that he is therefore without authority to ban them through regulation. Then Trump will punt the issue to Congress as he has with their issues.
I don’t see what it really accomplishes for him other than deferring the issue in the hope that it all blows over, while creating a convenient scapegoat if it doesn’t. Basically, the same thing he did with DACA.