Theoretically, can't a bulb be marked 'HB2', be also marked 'H4', be also marked with an ECE mark, but be not marked 'DOT'? Theoretically :)
Anyway,
From TSD No. 108, Revision 5R, "Lighting System and Retroreflective Devices (Standard 108)": (bolding mine)
From TSD No. 108.1, "Alternative...