Why do you think that? As the person you replied to said, the only reason the O-ring is there at all is to seal the joint between the sections. If the join't didn't exist, there would be no reason at all for there to be a rubber ring embedded in the structure.
Because that spot on the SRB is a flex joint to allow some movement of the nozzle as the engine fires. The joint isn't there because of transportation or other reasons.
I'm no rocket scientist either, but happened to be reading in depth about SRBs in general and Challenger in particular, and my understanding is: the joint in question was a field joint, to be assembled in the field, as opposed to factory joints which were assembled in the factory. The construction of these joints were different (asbestos insulation vs O-rings). The differing design is due to transportation and logistics.
And if the politicians didn't vote to build the SRBs in Utah, then maybe there would be no SRB at all, which is a good method to prevent deaths from SRBs.
