Actually, the ovaline shape of anamorphic bokeh has NOTHING to do with the shape of the front element. If it did, OP is right--the ovaline shape would be reversed after the de-squeeze in post.
Instead, the shape is due to one of the weird properties of shooting anamorphic. When you shoot with, say, a 100mm 2X anamorphic lens, you get a crop factor of effectively 50mm....in the left-right axis. In the up-down axis, however, you're still shooting effectively 100 mm. Since 100mm gives bigger boken than 50mm, your bokeh will be bigger in the up-down axis than in the left-right axis. Hence the oval shape.
