I work at a dealership, I was told the bolts are so the tool can be used to remove non-original oil filters that are smooth (don't have the notches around the top perimeter that the tool holds on to). The cup would be put on the top of the after-market filter, then the bolts tightened onto the filter through the threaded holes. The filter wrench can then be used to unscrew the filter. Wouldn't be a real good idea to put a new after-market filter on in this manner, though. Not all after-market filters are made in this manner, of course. Some have the notches.
I like the BMW filter wrench I bought for doing MB spin-on filters. It was originally purchased to do oil changes on mt K75S motorcycle. It fits the MB spin-ons, the reason I like it is no seperate socket is required, it has a 3/8" drive square hole on top, so only the tool, an extension and ratchet are required. It also has the hex end, so a socket could be also used, say if you have a tough one and want to go up to a 1/2" drive ratchet.
Gilly