Beam models are a very idealized model that ignores a lot of detail so that basic sizing calculations can be performed and the design iterations can be rapidly done.  Once the design has converged on a potentially feasible solution, a detailed model is often built to look at the stress around the actual welded connections between the truss ends.  The photo below shows welded ends. A detailed model could be built to analyse the stress, which will probably have higher stresses than the simple beam model due to stress concentrations.