We should probably be discussing this on another thread. Yes, that is the proper bed bracket for the taper attachment. I'm not an expert, but I'm guessing somebody drilled/tapped this one for the collet rack, or maybe some came that way from the factory. The taper attachment must be properly aligned to be exactly parallel with the bed in order to function accurately. So, you align it with a dial indicator, then slide the bed bracket onto the rod and the bed way, clamp it firmly on the bed way, then set it in the proper position on the rod with washers and nut. Then you pour molten babbit into one of the holes until it comes out the other hole and let it cool. Once cool, you can remove the bracket and put it back on again and still have the taper attachment in perfect alignment. To use the taper attachment you have to lock the bracket on the bed so that the cross slide will follow the angle set on the taper attachment, but while it is not in use, you loosen the bed bracket so that the whole taper attachment slides on the way as the saddle moves up and down the ways, which is why most folks simply remove it when not in use. Most hobbiests seldom use the taper attachment.
That square-head lock screw you have on yours is to lock a collet closer holder in place, not for adjusting the taper attachment rod.