I think it is realistic. It is from Primary Chronicle written in Old Church Slavonic by Nestor the Chronicler. Nestor the Chronicler was from Kiev and he lived in Kiev Rus' era. He spoke slavic language so he was not some kind of Germanic nationalist.
Common guys just becouse name Rus has germanic origin that dosent mean anything at all. French have germanic name and they dont mind that at all. Infact French always hated Germans and many still do.
French historic land, Normandy has similar germanic name. Italian Lombardy has germanic name. Scottish use germanic name Scotland (Alba was original name but they use Scotland nowdays). German name Brandenburg (name of german Länder) has origin from slavic Braniborska. Duchy of Prussia and later Kingdom of Prussia had Baltic name yet they werent Balt speaking countries.
Until 19th century national ideas didnt exist. People didnt care alot if their ruler was a Mongol, Viking, Slav or a Moor. I give you one example from Carniola a historic slovene land. In Carniola there were gottsche germans, they didnt think of themself as germans. They all considered themself as Carniolians not germans. Same goes for Slovenes in Carniola. Slovenes from other land like example Carinthia, considered themself as Carinthians not anything else.