it helps support the IC tubing cause its so heavy adn teh IC just hangs off the IC tubes, mine doesn't quite line up so I left mine out, the lower IC tube has 2 spots its held to the block so you will be fine without it.
Though not absolutely needed, it is a good idea to leave it on as it helps support the IC. I leave the stud in place and slot the hole so the tube can be taken off without any hassle.
I have a XXIC w/o the bolt. I prefer to have the bolt in there for support though. Might slot the hole so I can line up the raised top and IC tubing. I couldn't get it to line-up without removing the bolt.