This is like an I-shaped beam terminating into, and welded to, an I-shaped support "girder" (beams at 90 degrees to each other). Because the support girder, being I-shaped, has small torsional stiffness, the reaction delivered to it by the beam will be a vertical force, with little or no moment. All the connection stiffening in the world won't change that. Replace the I-shaped girder with a closed tubular shape and the connection now has the potential to transfer moment in addition to the vertical force.