Actually, it is not that uncommon to have the SSID for 2.4GHz and 5GHz to be the same. The problem is that not all WiFi clients are the same. What will happen is that the WiFi client will either prefer 5GHz, or just pick one at random and not band steer itself if the connection isn't good.
Aruba for example keeps all the SSIDs the same, and has a secret sauce to make sure that the clients are on the best AP and band.