But a 5th level character isn't a mere professional in the PHB and DMG guidelines. A 5th level character is a hero of the realm, and while future printings could change this definition, I don't think they should. A 5th level character, after all, is someone who can face monsters beyond any that exist in the real world or singlehandedly defeat a group of trained warriors. Meanwhile, I'd argue that 13th level characters, with the ability to raise the dead or teleport instantly across the world, qualify as epic by any reasonable definition.
If the developers don't want 5th level characters to be heroes of the realm and 13th level characters to be epic heroes, then they should be looking at changes to ability progression, not just labeling. Personally, I'd actually prefer such a system, with more levels of customization for a given degree of power progression. If such a change isn't on the table though, D&D should continue to recognize 5th level characters as the powerful figures they are and should give them access to bastion features (if such figures are going to be level-gated) appropriate to that status.