People are not able to derive the essence from the form. The form was Bulgarian, but the essence was Slavic. Or the state was Bulgaria but the Slavs consisted the population. Now when we have Bulgarians, are those people entitled to claim the entire Slavic history under the rule of the Bulgars? Or under the rule of Slavs which state was named Bulgaria? Whatever the game might be the only I can trust is the fact that Samoil was Brsjak (of course Vladislav and Garvilo) and the Brsjaks were/are Slavs not Bulgars nor present Bulgarians. 

In other words Basil II the "Bulgar-slayer" is the form, but Basil II the "Slav-slayer" is the essence.