You may interpret a line to fit your fantasy, but you can't change the historical fact that there is no Bosnian Slavic tribe and that king Tvrtko didn't crown himself as the King of Bosnians, Serbs etc. but as the King of the Serbs of Bosnia etc. (Kralj Srbljem, Bosne, Primorja i k tomu)

Tvrtko had a few titles throughout his reign. They were:

    [li]by the mercy of God Lord of many lands, Bosnia, and Soli and Usora and the Lower Edges and the Drina and the Hum Lord[/li]
    [li]by the mercy of God famous King of Rascia, Bosnia, Dalmatia, Croatia, the Seaside…[/li]
    [li]King of Serbs/Serbia, Bosnia, Pomorje, and the Western lands[/li]

Stefan Uros IV was crowned "Emperor of Serbs and Greeks". Does that mean he was Greek? or that Serbia was 50% Serbian, 50% Greek? Tvrtko was King of Serbs because he was related to the Nemanjic family.