tall spindles from a B body

I pulled these off today to convert the Nova to larger brakes, but when the crud started coming off they have a weird spot in the casting that appears to have piece broken off. Has anyone seen this before? The casting line is apparent on either side of the area as if something was there when cast. It will not affect the operation on the Nova and there was nothing I could see on the Oldsmobile that would have required a boss to be in this area